Using the base class wxHAS_NATIVE_ENABLED_MANAGEMENT in Cocoa

disabling/enabling child windows

Fixes #16232, fixes #15495.

(this is a backport of 91f25e0 from master)

include/wx/osx/cocoa/private.h

@@ -260,6 +260,7 @@ public :
     void            RestoreWindowLevel();
     
     static WX_NSResponder GetNextFirstResponder() ;
+    static WX_NSResponder GetFormerFirstResponder() ;
 protected :
     CGWindowLevel   m_macWindowLevel;
     WXWindow        m_macWindow;