[ticket/11997] Correctly redirect to front controllers

We currently do a lot of checks in order to prevent users from getting to
a 404 page. However, this logic relies on checking if a file or folder exists.
Due to the front controllers and the URL rewriting in 3.1, it is no longer
possible to rely on existing files for redirecting. This patch will take
care of properly redirecting users to front controller files. An incorrect
link will cause users to get a 404 error though.

PHPBB3-11997
[ticket/11997] Remove obsolete if statement in phpbb_own_realpath()

PHPBB3-11997
[ticket/11997] Rename root_dirs_size to superordinate_dirs_count

This variable name better fits what is done with it. A comment explaining
why 2 has to be subtracted from the size of root_dirs has also been added

PHPBB3-11997
[ticket/11997] Use $phpbb_filesystem->clean_path() for proper redirect paths

PHPBB3-11997
[ticket/11997] Fix redirects from inside controllers

The redirect url currently uses the web root path. However as we prepend the
full board url later, we need to remove the relative web root path and prepend
the normal root path again. Otherwise redirects from inside routes will not
work as intended.

PHPBB3-11997
[ticket/11997] Fix missing global

PHPBB3-11997
[ticket/11997] Add functional test for redirects in controller

PHPBB3-11997
Merge pull request #4 from nickvergessen/ticket/marc/11997

Ticket/marc/11997
[ticket/11997] Remove obsolete failover_flag in function redirect()

This flag is no longer needed as the failover is no longer needed.

PHPBB3-11997
[ticket/11963] Don't depend on user_notify flag to delete report notifications.

PHPBB3-11963
[ticket/11963] Delete topic_in_queue notifications in MCP approve_details mode

PHPBB3-11963
[ticket/11963] Fix undefined variable: post_data when mass-approving topics.

PHPBB3-11963
[ticket/12055] Alternate table row background colors using nth-child rule.

PHPBB3-12055
[ticket/12038] Check that the move action succeeded before moving the rows.

PHPBB3-12038
[ticket/12038] AJAXify move up/down buttons in the smilies/topic icons page.

PHPBB3-12038
[ticket/12038] AJAXify move up/down buttons in the module management pages.

PHPBB3-12038
[ticket/12038] AJAXify move up/down buttons in the permission roles page.

PHPBB3-12038
[ticket/12038] AJAXify move up/down buttons in custom profile fields page.

PHPBB3-12038
[ticket/12038] AJAXify move up/down buttons in report/denial reasons page.

PHPBB3-12038
[ticket/12038] Use $move_executed in place of $db->sql_affectedrows().

PHPBB3-12038