Allow building wxGTK under Windows with MSVC.

Replace a few more __WXMSW__ tests with __WINDOWS__ ones and modify bakefiles
to allow specifying the toolkit to be built in wxMSW makefiles.

Closes #13902.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73290 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/private.h

@@ -932,7 +932,7 @@ enum wxWinVersion
 
 WXDLLIMPEXP_BASE wxWinVersion wxGetWinVersion();
 
-#if wxUSE_GUI
+#if wxUSE_GUI && defined(__WXMSW__)
 
 // cursor stuff
 extern HCURSOR wxGetCurrentBusyCursor();    // from msw/utils.cpp
@@ -1069,6 +1069,6 @@ inline void *wxSetWindowUserData(HWND hwnd, void *data)
 
 #endif // __WIN64__/__WIN32__
 
-#endif // wxUSE_GUI
+#endif // wxUSE_GUI && __WXMSW__
 
 #endif // _WX_PRIVATE_H_