Make sure all code paths that use Temporal will initialize and reset it
properly. Some code paths (in tet runners) doesn't use Sessions, so
Temporal::reset() has to be invoked directly.
Just set the static superclock variable to 0 as initial value.
TempoMap will still be initialized early as a singleton, but we
introduce a new constructor so it is created empty (and thus not really
usable until Temporal::reset() or similar has populated it).
We can thus drop the static initialization of superclock. The default
superclock rate of 282240000 will now only live in Temporal::reset().
With this change there should no longer be any uninitialized use of
superclock_ticks_per_second(), and there should not be any problems for
DEBUG_EARLY_SCTS_USE to catch. (It is however broken in other ways -
that will be fixed next.)
91314b68a5