Fix the race condition when an interruption occured at the beginning
of thread_yield(), i.e.: just after SR(R2) was pushed but before
the rest of the suspended thread's context was pushed!
Make hwtimer_spin() work even with interrupts disabled
CoSenS port for RIOT
Reimplement CoSenS using messages, to minimize the use of hwtimers
Implementation of S-CoSenS for RIOT OS