This changes the destroy_link_manager() function to:
* call a new function message_get_unlock() to unlock the sending thread from
  its blocking message_get()
* calls pthread_cancel() on the receiving thread, because this unlocks any
  blocking read from a file descriptor

The same message_get_unlock() function has been added ringbuffer_queue to keep
the interfaces the same (it does nothing, because ringbuffer_queue is
non-blocking).

For whatever reason most of the files had their permission
changed from 644 to 755, which is not wanted.

log.c simplification, fix usefull functionality which never worked, move all log code from openair2 to common