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.)
Basically, if the paste position is not zero and not on a bar line, we will a BBT marker there,
using the existing tempo & meter at that position before the paste.
If the end of the paste is not on a bar line, we will place a BBT marker there,
using the tempo & meter that existed before the paste.
TempoMap::paste() now also accepts an optional final argument that if provided is
used to name the BBT markers, if they are created
the API now provides the option to call ::get_grid() with an iterator which may
be re-used on subsequent calls. This avoids unbounded O(N) "walks" from the
marker preceding the start point of the grid to the start point.
This commit also includes "fast-path" code for the common case of a single
tempo and single meter
These were not thread safe, and could not be: to be useful, a thread looking up a time
conversion could cache the result, but it would be using the global (shared) copy
of the map (because lookup is read-only, and so no write-copy is required). But
inserting into the lookup table wasn't lock protected (and shouldn't be because otherwise
that defeats the point of RCU).
So just drop it.