Changed how modules bind so that they can override existing variables

Upsilon/Binder/Binder.cs

@@ -252,7 +252,7 @@ namespace Upsilon.Binder
                             {
                                 if (moduleVariable.Value.Local)
                                     continue;
-                                Scope.Variables.Add(moduleVariable.Key, moduleVariable.Value);
+                                Scope.AssignToNearest(moduleVariable.Value);
                             }
                         }
                     }