cool#6616 compare graphics for equality with operator==...

instead of checking equal CheckSums.

For better or worse while Bitmap::operator== also considers equal
CheckSums as equal Bitmaps operator== can quickly return true if
both Bitmaps share the same underlying SalBitmap which is nearly
always true in the example here

Change-Id: I6b5cd484aeef7505721a493a3bff23ee345147dc
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155740
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>

filter/source/svg/svgwriter.cxx

@@ -2916,7 +2916,7 @@ void SVGActionWriter::ImplWriteBmp( const BitmapEx& rBmpEx,
         if (aGraphic.GetType() == GraphicType::Bitmap)
         {
             const BitmapEx& rGraphicBitmap = aGraphic.GetBitmapExRef();
-            if (rGraphicBitmap.GetChecksum() == rBmpEx.GetChecksum())
+            if (rGraphicBitmap == rBmpEx)
             {
                 bool bPNG = false;
                 GfxLink aGfxLink = aGraphic.GetGfxLink();