Event timer is presented.

Present new implementation of timer which uses event state machine for
invoking callbacks. Advantage of this method is easy and fast acces to timers
 from "user space".
Timers are powered by timerfd timers which uses kernel directly and at the
same time thes timers use file descriptor to indicate timeout. This 
implementation is exactly what the event machine need.
Fix make error caused by wrong _POSIX_C_SOURC.

C standart c11 (-std=c11) setts  _POSIX_C_SOURC to wrong value.
Add event_timer example.