Let calloc handle multiplication

It's going to multiply anyway, so if we have non-constant values, might
as well let it do the multiplication instead of adding another multiply,
and good versions of calloc will check for & avoid overflow in the process.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

Xext/panoramiXprocs.c

@@ -1106,7 +1106,7 @@ PanoramiXCopyArea(ClientPtr client)
         }
 
         pitch = PixmapBytePad(stuff->width, drawables[0]->depth);
-        if (!(data = calloc(1, stuff->height * pitch)))
+        if (!(data = calloc(stuff->height, pitch)))
             return BadAlloc;
 
         XineramaGetImageData(drawables, srcx, srcy,