tlist: Add heap based implementation of timer list

Previous timer was sorted list implementation of priority queue
and very slow when number of timers increased. This is mostly
not a problem because usually only few timers are used.
But for application where bigger number of timers are needed
it may become problem.

Solution is to use binary heap based priority queue which is much
faster.

API is unchanged, just timerlist_destroy is added which should be called
to free heap array. This function also destroys mutex (omitted when
mutex was added).

Signed-off-by: Jan Friesse <jfriesse@redhat.com>