[X11DRV] Re-add support for the 'UseXShm' config key.

[Alexandre Julliard]

Lionel Ulmer <lionel.ulmer at free.fr> writes:

> Well, sometimes, in some rare debugging cases, it's useful to have it, yeah.

But is it useful enough to justify exposing it, documenting it,
explaining to users they shouldn't touch it, etc.?  IOW do you use it
often enough that it's painful for you to have to modify the source
and rebuild to disable it?

-- 
Alexandre Julliard
julliard at winehq.com