[ticket/12407] Allow changing of post_data, etc. at end of posting.php

The current event core.posting_modify_template_vars is just ran using dispatch
but it doesn't pass any data from posting.php to the listener. Because of that,
it's not possible to know anything from posting.php and therefore limits the
use cases of this event. This will change it to allow similar actions as with
the event core.modify_posting_parameters.

PHPBB3-12407
[ticket/12407] Add message_parser as passed variable to event

PHPBB3-12407
Merge branch 'develop-ascraeus' of https://github.com/phpbb/phpbb into ticket/12407

Conflicts:
	phpBB/posting.php
[ticket/12407] Assign template variables again after merging develop-ascraeus

PHPBB3-12407
[ticket/12407] Merge @change in doc block of event

PHPBB3-12407
Merge branch 'develop-ascraeus' of github.com:phpbb/phpbb into ticket/12407

* 'develop-ascraeus' of github.com:phpbb/phpbb: (424 commits)
  [ticket/12428] Use the database to store the original version number
  [ticket/12493] Add functional test
  [ticket/12493] Fix sql query for selection of users that have disabled PM
  [ticket/12513] Add asset include support to simple header/footer in ACP
  [ticket/12513] Add simple_header head event with support for CSS assets calls
  [ticket/12511] Add missing titles for profile fields in members group view
  [ticket/12428] Incorrect from version in database update log entry
  [ticket/12510] Convert & to &amp; in build_url() when no params are stripped.
  [ticket/12402] CAPTCHA plugin migration fails to detect missing plugins
  [ticket/12440] Use a more generic approach for replacing the URL.
  [ticket/12507] Move the 'require' statement
  [ticket/12507] Add console command to purge the cache
  [ticket/12421] Rebase and enable tests
  [ticket/12421] Don't parse [attachment] tags if user can't view them
  [ticket/12325] Use \RecursiveDirectoryIterator
  [ticket/12325] Doc blocks
  [ticket/12440] Set browser URL to point to specific post when using view=unread
  [ticket/12357] Support routes in generate_smilies() function.
  [ticket/12459] Change language strings
  [ticket/12504] Use local variables where possible
  ...

Conflicts:
	phpBB/posting.php
[ticket/12407] Fix incorrect @since line in event

PHPBB3-12407
[ticket/12407] Remove merge marker from posting.php

PHPBB3-12407
Merge pull request #2306 from marc1706/ticket/12407

[ticket/12407] Allow changing of post_data, etc. at end of posting.php

* marc1706/ticket/12407:
  [ticket/12407] Remove merge marker from posting.php
  [ticket/12407] Fix incorrect @since line in event
  [ticket/12407] Merge @change in doc block of event
  [ticket/12407] Assign template variables again after merging develop-ascraeus
  [ticket/12407] Add message_parser as passed variable to event
  [ticket/12407] Allow changing of post_data, etc. at end of posting.php