Refactoring to common code for updating selections, using common focus

code

See #14269.

(this is a backport of e65104f from master)

include/wx/osx/cocoa/private/textimpl.h

@@ -48,7 +48,7 @@ public :
     virtual bool resignFirstResponder(WXWidget slf, void *_cmd);
 
     virtual void SetInternalSelection( long from , long to );
-
+    virtual void UpdateInternalSelectionFromEditor( wxNSTextFieldEditor* editor);
 protected :
     NSTextField* m_textField;
     long m_selStart;