cmLocalGenerator: Require a parent in the constructor.

Pass the parent though cmGlobalGenerator::CreateLocalGenerator.

This will make it easy to initialize state scopes independent of
cmMakefile.

Source/cmGlobalXCodeGenerator.h

@@ -41,7 +41,7 @@ public:
   static void GetDocumentation(cmDocumentationEntry& entry);
 
   ///! Create a local generator appropriate to this Global Generator
-  virtual cmLocalGenerator *CreateLocalGenerator();
+  virtual cmLocalGenerator *CreateLocalGenerator(cmLocalGenerator* parent = 0);
 
   /**
    * Try to determine system information such as shared library