ecore: Fix obvious crash with legacy timers

ecore_timer_del() checks a flag "inside_call" that can be
set before calling the timer cb... but it was never reset
to 0. So, all legacy timers would keep on ticking forever
and ever, until they return CANCEL.

Anyway, I find the distinction between eo_del and
ecore_timer_del very troubling. eo_del() should work
on a legacy timer. Ping @cedric. Maybe override eo_del()?

Fixes T3898

src/lib/ecore/ecore_timer.c

@@ -168,6 +168,8 @@ _ecore_timer_legacy_tick(void *data, const Eo_Event *event)
    if (!_ecore_call_task_cb(legacy->func, (void*)legacy->data) ||
        legacy->delete_me)
      eo_del(event->object);
+   else
+     legacy->inside_call = 0;
 }
 
 EO_CALLBACKS_ARRAY_DEFINE(legacy_timer,