ALSA & Dummy: implement port [un]registration_callback
ALSA backend: prevent possible crash destruction of a-r-d
ALSA rt-thread priority fixes
update for xjadeo 0.7.7 (don't connect to jackd by default)
check for xjadeo/xjremote >= 0.7.7
ALSA backend: separate systemic audio+midi latency
limit automation event density - fixes #5928

Constrain control points to one per tick (1/1920 beats).

Prior to this it was possible to set two values to the
same time (interpolation and iteration failed).