[ticket/11667] includeasset should be abstract

PHPBB3-11667
[ticket/11667] Make functions abstract in includeasset

Also comment properly

PHPBB3-11667
Merge branch 'develop' of github.com:phpbb/phpbb3 into ticket/11667

# By Joas Schilling (224) and others
# Via Andreas Fischer (23) and others
* 'develop' of github.com:phpbb/phpbb3: (385 commits)
  [ticket/11734] Readd accidently removed language strings of forum permissions
  [ticket/11620] Whitespace and combine function into test_case
  [ticket/11620] Move check_ban_test functions to setUp/tearDown for clarity
  [ticket/11620] Changed incorrect global variable
  [ticket/11620] Minor indentation changes and comment clarity
  [ticket/11733] Fix "Illegal offset type" Warning caused by overall feed
  [ticket/11733] Add browse test for feed.php
  [ticket/11731] Remove static calls to captcha garbage collector
  [ticket/11728] Replace topic_approved with topic_visibility
  [ticket/11620] Expected and actual test conditions wrongly swapped
  [ticket/11620] Space between . in directory import concatenation
  [ticket/11620] Changes to match merge
  [ticket/11620] Changes for code guidelines consistency
  [ticket/11620] Fix a static calls to non-static for session captcha
  [ticket/11620] Cleanup creation_test that was renamed on a cherry-pick
  [ticket/11620] Update auth_provider for new interface
  [ticket/11620] Added garbage_collection_test
  [ticket/11620] Fixed check_ban_test errors with cache and ban warning message
  [ticket/11620] Fixed a typo on check_ban_test
  [ticket/11620]  Refactored check_isvalid_test to use session_test_case
  ...
[ticket/11667] Use @inheritdoc

PHPBB3-11667
Merge remote-tracking branch 'EXreaction/ticket/11667' into develop

* EXreaction/ticket/11667:
  [ticket/11667] Use @inheritdoc
  [ticket/11734] Readd accidently removed language strings of forum permissions
  [ticket/11667] Make functions abstract in includeasset
  [ticket/11667] includeasset should be abstract