wxGrid focus handling fixes:

- don't allow focus in helper labels subwindows
- draw selection in different colour when not focused
- hide cursor/highlight when not focused



git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51313 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/grid.h

@@ -1625,6 +1625,8 @@ public:
 
     // override some base class functions
     virtual bool Enable(bool enable = true);
+    virtual wxWindow *GetMainWindowOfCompositeControl()
+        { return (wxWindow*)m_gridWin; }
 
 
     // ------ For compatibility with previous wxGrid only...