DoCanRead is protected in the base class, make it the same in derived classes.

include/wx/gifdecod.h

@@ -85,11 +85,12 @@ public:
     wxAnimationType GetType() const wxOVERRIDE
         { return wxANIMATION_TYPE_GIF; }
 
-private:
+protected:
     // wxAnimationDecoder pure virtual
     virtual bool DoCanRead( wxInputStream& stream ) const wxOVERRIDE;
         // modifies current stream position (see wxAnimationDecoder::CanRead)
 
+private:  
     int getcode(wxInputStream& stream, int bits, int abfin);
     wxGIFErrorCode dgif(wxInputStream& stream,
                         GIFImage *img, int interl, int bits);