If we only take the first commit, we leave a bunch in the queue, which
makes us that much more likely to run out of FDs when importing the
myriad of buffer referenced coming from a non-vsynced client. Fixes
crashes with vblank_mode=0 glxgears after the recent changes.
We were always subject to such crashes, just getting lucky/fast before.
This should make steamcompmgr messages actually go when we send them.
We're pulling too many frames out of "vsynced" clients now, need to instill
a real frame cadence based on vblank and notify based on that.
frames out of thin air.
Also use dummy ClientMessage events to nudge steamcompmgr's event loop,
Expose events have a meaning and we don't want to confuse some clients.