gitlab migration

[Adam Jackson]

I'd like us to start moving repos and bug tracking into gitlab.
Hopefully everyone's aware that gitlab exists and why fdo projects are
migrating to it. If not, the thread about Mesa's migration provides
some useful background:

https://lists.x.org/archives/mesa-dev/2018-May/195634.html

This should be mostly mechanical, except for moving some of the older
junk into the archive and deciding which drivers _not_ to move yet (I
imagine intel has some of its processes hooked up to bz, for example).

As far as contribution model, I'd personally prefer to stop using
mailing lists, and for most of the X components I expect that's
probably an improvement, because most components do not have especially
active maintenance and it's currently very easy for patches to get lost
in the mailing list history. Conversely for the server it can be
difficult to keep track of a patch series' approval state. Again, not
solely my decision to make, so I'd like to hear some rough consensus on
how to proceed. Anyone with strong opinions, please do speak up.

- ajax