This adds a new interface to the swrast interface to fix an shm put image bug.

The current code adds the x,y src offsets into the offset parameters,
however if the x offset is > 0, and the put image copies up to the height
of the image, this can trigger an X server validation check to fail and
the renderering to get BadMatch.

This patch fixes it to pass the x offset coord in as a src x.

We cannot pass the Y coordinate due to the horrible code mangling the
image w/h vs stride in swrastXPutImage.

v2: drop srcx,y from api

Cc: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Adam Jackson <ajax@redhat.com>