drisw: Port the MIT-SHM check to XCB

The old version isn't thread-safe, and xlib makes it unreasonably
difficult to write thread-safely.

Fixes: mesa/mesa#3398
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6294>
5 files changed