Qt: Drop QtMultimedia dependency if SDL is used. Force OSX10.9 SDK. Should fix #5835
Correct cyclesLate if an event consumes cycles.

This can prevent things from drifting out of sync.
Fix periodic events drifting when eating cycles.

Need to set the next timer before rescheduling threads or etc.
Add some missing algorithm includes.
Fix a potential crash/race condition.

If anything is behind, it might run __AudioWakeThreads() within
reschedule, and get confused.