Gui: Cleanup legacy code.

src/Gui/Selection/Selection.h

@@ -185,33 +185,7 @@ public:
     const SelectionChanges *pOriginalMsg = nullptr;
 };
 
-} //namespace Gui
-
-
-
-// Export an instance of the base class (to avoid warning C4275, see also
-// C++ Language Reference/General Rules and Limitations on MSDN for more details.)
-//
-// For compiler gcc4.1 we need to define the template class outside namespace 'Gui'
-// otherwise we get the compiler error:
-// 'explicit instantiation of 'class Base::Subject<const Gui::SelectionChanges&>'
-// in namespace 'Gui' (which does not enclose namespace 'Base')
-//
-// It seems that this construct is not longer needed for gcc4.4 and even leads to
-// errors under Mac OS X. Thus, we check for version between 4.1 and 4.4.
-// It seems that for Mac OS X this can be completely ignored
-
-#if defined(__GNUC__) && defined(__GNUC_MINOR__) && !defined(FC_OS_MACOSX)
-#define GNUC_VERSION (((__GNUC__)<<16)+((__GNUC_MINOR__)<<8))
-#if GNUC_VERSION >= 0x040100 && GNUC_VERSION < 0x040400
-template class GuiExport Base::Subject<const Gui::SelectionChanges&>;
-#endif
-#undef GNUC_VERSION
-#endif
-
-namespace Gui
-{
-    class ViewProviderDocumentObject;
+class ViewProviderDocumentObject;
 
 /**
  * The SelectionObserver class simplifies the step to write classes that listen