The timer code used to trigger periodic statistics message sending used
ITTI. Together with a high frequency reporting (e.g. 1ms), this resulted
in high CPU usage. This commit reimplements this:
* using a thread that is synchronized to the RU (if there is no MAC, we
assume there is no RU generating a tick so we create the tick source
ourselves)
* no RB trees but plain arrays
* smaller interface for users
* slight user interface changes
* remove stopped timer state: such timer might be simply removed
* remove one-shot timers
Robert Schmidt
b6d466d772