v.category: add keyword layer

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@56303 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.category/main.c

@@ -74,6 +74,7 @@ int main(int argc, char *argv[])
     module = G_define_module();
     G_add_keyword(_("vector"));
     G_add_keyword(_("category"));
+    G_add_keyword(_("layer"));
     module->description =
 	_("Attaches, deletes or reports vector categories to map geometry.");