r.contour: fix an error message text (#1014)

The incorrect message was:
> r.contour input=x output=y
ERROR: Neither <levels> nor <step> option must be specified

At least one of the options must be specified. Exactly one option should
be specified (specifying both is currently the same as specifying
"levels" only). Fix the message to say what was originally intended.

locale/po/grassmods_ar.po

@@ -12241,7 +12241,7 @@ msgstr "عرض قائمة مستويات الكنتور"
 
 #: ../raster/r.contour/main.c:140
 #, fuzzy, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr "طبقتين يجب تحديدهم"
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_bn.po

@@ -10738,7 +10738,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_cs.po

@@ -10770,7 +10770,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_de.po

@@ -10750,7 +10750,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_el.po

@@ -10746,7 +10746,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_es.po

@@ -10761,7 +10761,7 @@ msgstr "Niveles de contorno"
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr "Ni la opción <%s> ni <%s> deben ser especificadas"
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_fi.po

@@ -10739,7 +10739,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_fr.po

@@ -10752,7 +10752,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_hu.po

@@ -10738,7 +10738,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_id_ID.po

@@ -10730,7 +10730,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_it.po

@@ -10757,7 +10757,7 @@ msgstr "Livelli delle isoipse"
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_ja.po

@@ -10743,7 +10743,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_ko.po

@@ -10734,7 +10734,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_lv.po

@@ -11287,7 +11287,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_ml.po

@@ -10738,7 +10738,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_pl.po

@@ -10762,7 +10762,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_pt.po

@@ -10744,7 +10744,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_pt_BR.po

@@ -10740,7 +10740,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_ro.po

@@ -10752,7 +10752,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_ru.po

@@ -10754,7 +10754,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_si.po

@@ -10738,7 +10738,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_sl.po

@@ -12363,7 +12363,7 @@ msgstr "Spisek vrednosti plastnic"
 
 #: ../raster/r.contour/main.c:140
 #, fuzzy, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr "navedena morata biti 2 sloja"
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_ta.po

@@ -10740,7 +10740,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_th.po

@@ -10733,7 +10733,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_tr.po

@@ -10746,7 +10746,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_uk.po

@@ -10754,7 +10754,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_vi.po

@@ -10733,7 +10733,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_zh.po

@@ -10733,7 +10733,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:183 ../raster/r.stream.extract/close.c:194

locale/po/grassmods_zh_CN.po

@@ -8683,7 +8683,7 @@ msgstr ""
 
 #: ../raster/r.contour/main.c:140
 #, c-format
-msgid "Neither <%s> nor <%s> option must be specified"
+msgid "Either <%s> or <%s> option must be specified"
 msgstr ""
 
 #: ../raster/r.contour/main.c:188 ../vector/v.reclass/main.c:322

raster/r.contour/main.c

@@ -138,7 +138,7 @@ int main(int argc, char *argv[])
 	exit(EXIT_FAILURE);
 
     if (!levels->answers && !step->answer) {
-        G_fatal_error(_("Neither <%s> nor <%s> option must be specified"),
+        G_fatal_error(_("Either <%s> or <%s> option must be specified"),
                       levels->key, step->key);
     }