Document that HasFocus() is new in 2.9.

Closes #14740.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72670 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/window.h

@@ -385,6 +385,8 @@ public:
         Returns @true if the window (or in case of composite controls, its main
         child window) has focus.
 
+        @since 2.9.0
+
         @see FindFocus()
     */
     virtual bool HasFocus() const;