clean features of all layers by default

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@39976 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.clean/main.c

@@ -48,6 +48,7 @@ int main(int argc, char *argv[])
 
     in_opt = G_define_standard_option(G_OPT_V_INPUT);
     field_opt = G_define_standard_option(G_OPT_V_FIELD_ALL);
+    field_opt->answer = "-1";
     field_opt->guisection = _("Selection");
     type_opt = G_define_standard_option(G_OPT_V3_TYPE);
     type_opt->guisection = _("Selection");