Using timers to target unspecified problems

This is a part of Advanced Gtk+ Sequencer out of ags_async_queue.h

#define AGS_ASYNC_QUEUE_CLOCK_ID CLOCK_REALTIME
#define AGS_ASYNC_QUEUE_SIGNAL_HIGH SIGRTMAX
#define AGS_ASYNC_QUEUE_SIGNAL_LOW SIGRTMIN

Instead queueing nanosleep there will be timers used. Another interesting function is pthread_yield() which relinquishes the cpu.