[ticket/8610] Update Bookmarks when merging topics

Update bookmarks to the new topic when merging multiple topics using
the merge_topics function.

PHPBB3-8610
[ticket/8610] Update Bookmarks when forking topics

Update bookmarks to the new topic when forking topics using
the mcp_fork_topic function.

PHPBB3-8610
[ticket/8610] Update Bookmarks when merging posts into another topic

Update bookmarks to the new topic when merging posts into another topic
using the merge_posts function.

PHPBB3-8610
[ticket/8610] Update Bookmarks and Subscriptions when splitting topics

Update bookmarks and subscriptions to add bookmarks/subscriptions to the
new topic when using the split_topic function

PHPBB3-8610
[ticket/8610] Add some comments

PHPBB3-8610
[ticket/8610] Revert some funky merging I did from rebase

PHPBB3-8610
[ticket/8610] Use phpbb_update_rows_avoiding_duplicates

PHPBB3-8610
Merge branch 'develop-olympus' of github.com:phpbb/phpbb3 into ticket/8610

# By Oleg Pudeyev (29) and others
# Via Andreas Fischer (3) and others
* 'develop-olympus' of github.com:phpbb/phpbb3: (36 commits)
  [ticket/11262] Add .lock in cache directory to .gitignore
  [ticket/11265] Add assertions for board installation success.
  [ticket/11162] Reformat.
  [ticket/10491] Make recreate_database static.
  [ticket/11162] Rename tricky updates to database helper.
  [ticket/10491] Install board once per test run.
  [ticket/10972] Drop user deletion.
  [ticket/10972] Tweak user addition.
  [ticket/10972] Add destroy method to mock cache.
  [ticket/10972] Add mock null cache.
  [ticket/10972] Backport get_db from develop.
  [ticket/10972] Added explicit checks for creating duplicate users.
  [ticket/10972] Moved tests into appropriate places and added comments
  [ticket/10972] Added methods for creating and deleting basic users
  [ticket/11162] Use empty($queries).
  [ticket/11162] Review comments fixed.
  [ticket/11162] Reformat.
  [ticket/11162] Newlines to LF.
  [ticket/11162] Use correct functions.
  [ticket/11162] Account for notify_status.
  ...

Conflicts:
	phpBB/includes/mcp/mcp_topic.php
[ticket/8610] Create helper functions to create topic/post in functional tests

This will be used to test splitting/copying/merging/etc in functional tests

Also convert functional posting_test.php to use these functions

PHPBB3-8610
[ticket/8610] Move posting helpers to separate file

This is to prevent cluttering up the functional test case class more

PHPBB3-8610
[ticket/8610] Do not use requests to submit posts except in posting_test.php

Moving my functional test functions from posting_helpers.php to
posting_test.php since it is a bit nicer and more reusable if
posting_test.php is to be expanded in the future.

PHPBB3-8610
[ticket/8610] Update comment

PHPBB3-8610
Merge PR #1140 branch 'EXreaction/ticket/8610' into develop-olympus

* EXreaction/ticket/8610:
  [ticket/8610] Update comment
  [ticket/8610] Do not use requests to submit posts except in posting_test.php
  [ticket/8610] Move posting helpers to separate file
  [ticket/8610] Create helper functions to create topic/post in functional tests
  [ticket/8610] Use phpbb_update_rows_avoiding_duplicates
  [ticket/8610] Revert some funky merging I did from rebase
  [ticket/8610] Add some comments
  [ticket/8610] Update Bookmarks and Subscriptions when splitting topics
  [ticket/8610] Update Bookmarks when merging posts into another topic
  [ticket/8610] Update Bookmarks when forking topics
  [ticket/8610] Update Bookmarks when merging topics