Convert events to have an associated pool.

* server/mpm/simple/simple_types.h
    (simple_timer_t): Add Pool and a pointer to the associated simple core.
    (simple_core_t): Remove dead timer ring, no recycling of timer events for now.

* server/mpm/simple/simple_event.h: Update register_timer signature with pool.

* server/mpm/simple/simple_event.c
    (simple_register_timer): Allocate the event structure out of the pool,
        and when this pool is destroyed, unregister the timer.
    (simple_timer_run): New util function for running a timer and cleaning up 
        the pool callbacks.

* server/mpm/simple/simple_core.c
    (simple_core_init): Remvoe dead timer ring

* server/mpm/simple/simple_run.c
    (simple_main_setup_timers): Pass in pool to register call.
    (simple_timer_invoke): Use new simple_timer_run function.
    (simple_child_loop): Remove dead timer ring.

* server/mpm/simple/simple_io.c
    (simple_io_process): Pass in pool when registering timers.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@709657 13f79535-47bb-0310-9956-ffa450edef68