i.cluster: define gisprompt for seeds

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@58472 15284696-431f-4ddb-bdfa-cd5b030d7da7

imagery/i.cluster/main.c

@@ -107,6 +107,7 @@ int main(int argc, char *argv[])
     parm.seed_sig->required = NO;
     parm.seed_sig->type = TYPE_STRING;
     parm.seed_sig->key_desc = "name";
+    parm.seed_sig->gisprompt = "old,sig,sigfile";
     parm.seed_sig->description = _("Name of file containing initial signatures");
 
     parm.sample_interval = G_define_option();