v.generalize: +warning about ignored where and cats options; reduce compiler warnings

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@73673 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.generalize/main.c

@@ -358,6 +358,10 @@ int main(int argc, char *argv[])
     if (layer > 0)
 	cat_list = Vect_cats_set_constraint(&In, layer, 
 			      where_opt->answer, cat_opt->answer);
+    else if (where_opt->answer || cat_opt->answer) {
+	G_warning(_("No layer selected, '%s' and '%s' options are ignored"),
+	          where_opt->key, cat_opt->key);
+    }
 
     if (method == DISPLACEMENT) {
 	/* modifies only lines, all other features including boundaries are preserved */