In order to get all focus set events, store field in editor and catch

becomeFirstResponder there

See #14269.

(this is a backport of cea11b5 from master)

include/wx/osx/cocoa/private.h

@@ -324,8 +324,10 @@ public:
     @interface wxNSTextFieldEditor : NSTextView
     {
         NSEvent* lastKeyDownEvent;
+        NSTextField* textField;
     }
 
+    - (void) setTextField:(NSTextField*) field;
     @end
 
     @interface wxNSTextField : NSTextField wxOSX_10_6_AND_LATER(<NSTextFieldDelegate>)