add the wxAnimation ctor which was documented but not present (backport of r52640 from trunk)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@58307 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/animate.h

@@ -27,6 +27,8 @@ typedef struct _GdkPixbufAnimationIter GdkPixbufAnimationIter;
 class WXDLLIMPEXP_ADV wxAnimation : public wxAnimationBase
 {
 public:
+    wxAnimation(const wxString &name, wxAnimationType type = wxANIMATION_TYPE_ANY)
+        : m_pixbuf(NULL) { LoadFile(name, type); }
     wxAnimation(GdkPixbufAnimation *p = NULL);
     wxAnimation(const wxAnimation&);
     ~wxAnimation() { UnRef(); }