replaced 'archimedean' with 'arcm::in()'

nonisotropic.cpp

@@ -1384,7 +1384,7 @@ EX namespace product {
   EX bool validate_spin() {
     if(prod) return hybrid::in_underlying_geometry(validate_spin);
     if(penrose) return false;
-    if(!quotient && !archimedean) return true;
+    if(!quotient && !arcm::in()) return true;
     map<cell*, cellwalker> cws;
     manual_celllister cl;
     cell *start = currentmap->gamestart();