[ticket/11754] Remove styleswitcher leftovers

PHPBB3-11754
[ticket/11760] Use phpbb_version_compare() wrapper

PHPBB3-11760
[ticket/11770] Fix class name for pm list

PHPBB3-11770
[ticket/11775] Fix error when moving the last post to another topic

PHPBB3-11775
[ticket/11775] Backport moving of the posting functions to 3.0

PHPBB3-11775
[ticket/11775] Add functional test for moving the last post

PHPBB3-11775
[ticket/11779] Fix unapproved messages class name

PHPBB3-11779
[ticket/11780] Remove unused images

PHPBB3-11780
[ticket/11780] Remove references to unused images

PHPBB3-11780
[ticket/11781] Include func update_post_information()

Include functions_posting before using functions defined in that file

PHPBB3-11781
[ticket/11777] Add subdirectory 'events/' to the template event search path

Makes the twig template engine look in the events/ subdirectory instead of the
main styles/[style]/template/ directory for extension template events. Note
that it does _not_ look recursively!

PHPBB3-11777
[ticket/11777] Move the testing template events to 'events/' subdirectories

The tests written for extension template events did not follow the convention
and documentation of placing template event files in the events/ subdirectory.
Moved the files to this subdirectory so the tests succeed again.

PHPBB3-11777
[ticket/11777] Rename the extension template listener subdirectory to 'event/'

Per suggestion of EXreaction and nickvergessen, do not look for extension
template event listeners in styles/[style]/template/events/ but in
styles/[style]/template/event/ (without the trailing 's') to match the way
phpBB looks for php template event listeners.

PHPBB3-11777
[ticket/11777] Require a suffix of '_listener' on extension template listeners

To further mirror the file name and location requirements for php template
event listeners, require extension template event listener files to follow the
'<event name>_listener.html' naming format.

PHPBB3-11777
[ticket/11777] Fix new test for loop variables in extension template listeners

With the merge of https://github.com/phpbb/phpbb3/pull/1564 a new test has
been added. Renamed and moved the template listener file of that test to
comply with the new requirements.

PHPBB3-11777
Merge remote-tracking branch 'cyberalien/ticket/11780' into develop

* cyberalien/ticket/11780:
  [ticket/11780] Remove references to unused images
  [ticket/11780] Remove unused images
Merge remote-tracking branch 'cyberalien/ticket/11781' into develop

* cyberalien/ticket/11781:
  [ticket/11781] Include func update_post_information()
Merge pull request #1643 from rechosen/ticket/11777

[ticket/11777] Search for template listeners in the php event listeners way
[ticket/11775] Split test into multiple steps

PHPBB3-11775
[ticket/11784] Remove naming redundancy for event listeners

PHPBB3-11784