findHooks.php: Use recursive directory iterator

findHooks.php: Use recursive directory iterator

The following dirs were not previously included:
* includes/compat/
* includes/compat/normal/
* includes/composer/
* includes/config/
* includes/db/loadbalancer/
* includes/debug/logger/
* includes/filebackend/filejournal/
* includes/filebackend/lockmanager/
* includes/jobqueue/aggregator/
* includes/jobqueue/jobs/
* includes/jobqueue/utils/
* includes/libs/
* includes/objectcache/
* includes/pager/
* includes/poolcounter/
* includes/profiler/output/
* includes/profiler/
* includes/registration/
* includes/templates/
* includes/tidy/
* includes/title/
* includes/utils/iterators/
* includes/widget/
* maintenance/ subdirectories

Change-Id: I6c01b8768f9f70152e320d254f8025a0ffde8c62