[ticket/11540] Add unit tests for is_absolute()

PHPBB3-11540
Merge remote-tracking branch 'nickvergessen/ticket/11540' into develop-olympus

* nickvergessen/ticket/11540:
  [ticket/11540] Add unit tests for is_absolute()
Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/11540] Add unit tests for is_absolute()
[ticket/11540] Add phpbb_ prefix in is_absolute_test from olympus.

PHPBB3-11540
Merge remote-tracking branch 'bantu/ticket/11540' into develop

* bantu/ticket/11540:
  [ticket/11540] Add phpbb_ prefix in is_absolute_test from olympus.