[ticket/13241] Add a functional test for viewforum with global announcement

PHPBB3-13241
[ticket/13241] Correctly ignore announcements from topics list

PHPBB3-13241
[ticket/13241] Fix pagination with global announcements

PHPBB3-13241
[ticket/13241] Sleep for 1 second when posting twice in the same second

PHPBB3-13241
[ticket/13241] Remove sleep() since the method takes care of this now

PHPBB3-13241
[ticket/13241] Remove sleep() and change flood interval instead

PHPBB3-13241