debug: add wrapper for pthread_create to add a meaningful name

This is very useful for debugging. Though tbh I need to do this code
properly.
subscriptions: stop re-entrant call to subs_reschedule()

THe problem is that mux subs have been done such that unsubscribe
(which in turn calls subs_reschedule()) can itelf be called in line
from subs_reschedule().

Really this is a bit of a mess but this simple hack fixes things.
mpegts: ensure muxes are properly stopped when unsubscribing svcs