Revert "[ft] Fix memory bug in copying bitmaps"

This reverts commit a0f556f37f.

The change was clearly wrong now that I read.  I was probably
tricked by what was fixed in the follow-up commit
e738079302.

src/cairo-ft-font.c

@@ -1161,7 +1161,9 @@ _get_bitmap_surface (FT_Bitmap		     *bitmap,
 		source = bitmap->buffer;
 		dest = data;
 		for (i = height; i; i--) {
-		    memcpy (dest, source, stride);
+		    memcpy (dest, source, bitmap->pitch);
+		    memset (dest + bitmap->pitch, '\0', stride - bitmap->pitch);
+
 		    source += bitmap->pitch;
 		    dest += stride;
 		}