Since XCB 1.10 the sync extension is working properly. At the time of
the 5.3 release 1.10 will have been out for ~15 months, enough time
for distros to catch up and should allow us to use it.

As our CI system only supports 1.9 at the moment we cannot hard depend
on the version, instead we use feature info. As soon as our CI system
supports it, we should update the required min version and kick out the
ifdef.

REVIEW: 122377