Can events be applied to LITMUS code instead of sched_task_trace ?

PROS:
	- architectural indipendency
	- easy porting on newer kernel version
	- lock free ring buffer implementation already there

CONS:
	- need userspace tools conversion to slightly different format
	- is it possible to replicate all the previous functionalities?
	- only sched_trace_* functions can be implemented through events,
	  TRACE() debugging features are still implemented in the old way
	  (??? cannot we simply use the tracing features of the kernel for
	   debugging purposes ????)

 - add syscall on x86_64
 - refactor __NR_sleep_next_period -> __NR_complete_job
   for both x86_32 and x86_64

to be merged:
 - arm_release_timer() with no rq locking