simplifications and corrections to background drawing:

1. removed ApplyParentThemeBackground() not used any longer
2. removed ProvidesBackground() which is synonymous with
   !HasTransparentBackground()
3. removed a whole bunch of unused MSWXXX() methods
4. moved MSWControlColor() from wxWindow up to wxControl

results:

1. the gradient is still shown properly for static/radio boxes in notebooks
2. correct background colour is used for the static boxes
3. code is shorter and better commented


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@33474 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/button.h

@@ -54,13 +54,6 @@ public:
     virtual WXLRESULT MSWWindowProc(WXUINT nMsg, WXWPARAM wParam, WXLPARAM lParam);
     virtual bool MSWCommand(WXUINT param, WXWORD id);
 
-    virtual void ApplyParentThemeBackground(const wxColour& bg)
-    {
-        // avoide switching into owner-drawn mode
-        wxControl::SetBackgroundColour(bg);
-    }
-
-#ifdef __WIN32__
     // coloured buttons support
     virtual bool SetBackgroundColour(const wxColour &colour);
     virtual bool SetForegroundColour(const wxColour &colour);
@@ -69,7 +62,6 @@ public:
 
 private:
     void MakeOwnerDrawn();
-#endif // __WIN32__
 
 protected:
     // send a notification event, return true if processed