Fix base location of the bitmap Wallpaper computation.

The nX / nY is correct for clipping operation, but not for base; visible with
WALLPAPER_TOPRIGHT style.

Change-Id: I8de92b68b822a156bc376201e97ce458d1a6ba08

vcl/source/gdi/outdev6.cxx

@@ -848,8 +848,8 @@ void OutputDevice::ImplDrawBitmapWallpaper( long nX, long nY,
     }
     else
     {
-        aPos = Point( nX, nY );
-        aSize = Size( nWidth, nHeight );
+        aPos = Point( 0, 0 );
+        aSize = Size( mnOutWidth, mnOutHeight );
     }
 
     mpMetaFile = NULL;