Fix inheritance of wxBitmapHelpers::Rescale as is needed on OpenVMS

include/wx/gtk1/bitmap.h

@@ -123,6 +123,8 @@ public:
 
     // Basically, this corresponds to Win32 StretchBlt()
     wxBitmap Rescale( int clipx, int clipy, int clipwidth, int clipheight, int width, int height );
+    // OpenVMS needs the next statement to detect Rescale in an inherited class
+    using wxBitmapHelpers::Rescale;
 
     // raw bitmap access support functions
     void *GetRawData(wxPixelDataBase& data, int bpp);