Deprecate useless wxGenericImageList::Create() overload

This overload doesn't do anything and doesn't exist in the MSW version,
so deprecate it.

src/generic/imaglist.cpp

@@ -49,11 +49,6 @@ bool wxGenericImageList::Create( int width, int height, bool WXUNUSED(mask), int
 {
     m_size = wxSize(width, height);
 
-    return Create();
-}
-
-bool wxGenericImageList::Create()
-{
     return true;
 }