Use GetAnimation() in wxAnimationCtrlXmlHandler again

This function basically only exists in order to be used in this handler,
so extend it to allow doing it by adding wxAnimationCtrlBase argument to
it, allowing it to create wxAnimation object compatible with the given
control.

This reduces code duplication and, incidentally, makes GetAnimation()
more useful for any user-defined XRC handlers.

interface/wx/xrc/xmlres.h

@@ -542,8 +542,15 @@ protected:
 
     /**
         Creates an animation (see wxAnimation) from the filename specified in @a param.
+
+        It is recommended to provide @a ctrl argument to this function (which
+        is only available in wxWidgets 3.1.4 or later) to make sure that the
+        created animation is compatible with the specified control, otherwise a
+        wxAnimation object compatible with the default wxAnimationCtrl
+        implementation is created.
     */
-    wxAnimation* GetAnimation(const wxString& param = "animation");
+    wxAnimation* GetAnimation(const wxString& param = "animation",
+                              wxAnimationCtrlBase* ctrl = NULL);
 
     /**
         Gets a bitmap.