Refactoring to common code for focus set and lost events, so that

changes can be made a single place

See #14269.

(this is a backport of 2b99f92 from master)

include/wx/osx/cocoa/private.h

@@ -129,6 +129,8 @@ public :
     virtual bool        DoHandleMouseEvent(NSEvent *event);
     virtual bool        DoHandleKeyEvent(NSEvent *event);
     virtual bool        DoHandleCharEvent(NSEvent *event, NSString *text);
+    virtual void        DoNotifyFocusSet();
+    virtual void        DoNotifyFocusLost();
     virtual void        DoNotifyFocusEvent(bool receivedFocus, wxWidgetImpl* otherWindow);
 
     virtual void        SetupKeyEvent(wxKeyEvent &wxevent, NSEvent * nsEvent, NSString* charString = NULL);