Add static wxAnimationCtrl::CreateCompatibleAnimation()

This may be more convenient to use than CreateAnimation() if there is no
wxAnimationCtrl object at hand.

include/wx/generic/animate.h

@@ -64,6 +64,8 @@ public:
     // override base class method
     virtual bool SetBackgroundColour(const wxColour& col) wxOVERRIDE;
 
+    static wxAnimation CreateCompatibleAnimation();
+
 public:     // event handlers
 
     void OnPaint(wxPaintEvent& event);