Fix g++ warnings about initialized variables being declared extern.

Don't declare variables extern when initializing them, this is already the
case implicitly anyhow and explicit "extern" results in g++ warnings.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67973 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/window.cpp

@@ -186,7 +186,7 @@ extern wxMenu *wxCurrentPopupMenu;
 // This is a hack used by the owner-drawn wxButton implementation to ensure
 // that the brush used for erasing its background is correctly aligned with the
 // control.
-extern wxWindowMSW *wxWindowBeingErased = NULL;
+wxWindowMSW *wxWindowBeingErased = NULL;
 #endif // wxUSE_UXTHEME
 
 namespace