Check for and prefer libev over libevent and check for the location
of the event.h file, which is contained in libev/event.h on Fedora.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Make sure dect_timer_running() returns the proper result for timers that
have already expired by adding a new function to invoke the timer callback
that resets the state to DECT_TIMER_STOPPED before invoking the callback.
Additionally unexport the timer structure and add an accessor function
for the private storage area to make sure all timer invocations happen
through the new function.
Signed-off-by: Patrick McHardy <kaber@trash.net>