Since now we don't set the swap throttled value based
on sync-to-vblank, we can effectively remove it from
Cogl. Throttling swap buffers in Cogl is as much a
historical artifact as sync-to-vblank. Furthermore,
it doesn't make sense to disable it on a compositor,
which is the case with the embedded Cogl.
In addition to that, the winsys vfunc for updating
whenever swap throttling changes could also be removed,
since swap throttling is always enabled now.
Removing it means less code, less branches when running,
and one less config option to deal with.
This also removes the micro-perf test, since it doesn't
make sense for the case where Cogl is embedded into the
compositor.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/191
This macro was introduced so as to be able to be built without GLib.
However, this feature was long ago removed, and in Mutter we depend on
it anyway, so let's get rid of it in favor of more consistency.
