[ticket/12551] Float breadcrumbs to the right in RTL languages.

PHPBB3-12551
[ticket/12549] Hide topic/forum list <dfn> tags in RTL languages.

PHPBB3-12549
[ticket/12550] Prevent last post column from jumping to second line in RTL.

PHPBB3-12550
[ticket/12555] Allow to set canonical URLs to avoid duplicate content

PHPBB3-12555
[ticket/12555] Add canonical URl for memberlist mode=viewprofile

Avoids duplicate content of:
* memberlist.php?mode=viewprofile&u=user_id
* memberlist.php?mode=viewprofile&un=username

PHPBB3-12555
[ticket/12555] Add canonical URL for viewforum

Avoids duplicate content of:
* viewforum.php?f=forum_id
* viewforum.php?f=forum_id&start=0

PHPBB3-12555
[ticket/12555] Add canonical URL for viewtopic

Avoids duplicate content of:
* viewtopic.php?t=topic_id
* viewtopic.php?f=forum_id&t=topic_id
* viewtopic.php?f=forum_id&t=topic_id&hilit=highlight_string
* viewtopic.php?f=forum_id&t=topic_id&view=unread
* viewtopic.php?f=forum_id&p=post_id
* viewtopic.php?f=forum_id&t=topic_id&start=0

PHPBB3-12555
[ticket/12576] Remove cron from common.php

PHPBB3-12576
[ticket/12576] Retrieve the cron_manager in cron.php if needed

PHPBB3-12576
[ticket/12572] Fix JS error when alert message title is undefined

JS console reports error in core.js:
TypeError: alert is undefined
alert.hide()
when res.MESSAGE_TITLE is undefined.

PHPBB3-12572
[ticket/12586] Use dot filter when trying to find available extensions

PHPBB3-12586
[ticket/12586] Limit depth to 2, we require vendor/extension/ext.php

PHPBB3-12586
Merge pull request #2491 from nickvergessen/ticket/12586

Ticket/12586 Filter files and depth when looking for extensions

* nickvergessen/ticket/12586:
  [ticket/12586] Limit depth to 2, we require vendor/extension/ext.php
  [ticket/12586] Use dot filter when trying to find available extensions
Merge pull request #2484 from Nicofuma/ticket/12576

[ticket/12576] Remove cron from common.php

* Nicofuma/ticket/12576:
  [ticket/12576] Retrieve the cron_manager in cron.php if needed
  [ticket/12576] Remove cron from common.php
Merge pull request #2465 from prototech/ticket/12549

[ticket/12549] Hide topic/forum list <dfn> tags in RTL languages.

* prototech/ticket/12549:
  [ticket/12549] Hide topic/forum list <dfn> tags in RTL languages.
Merge pull request #2466 from prototech/ticket/12550

[ticket/12550] Prevent last post column from jumping to second line in RTL.

* prototech/ticket/12550:
  [ticket/12550] Prevent last post column from jumping to second line in RTL.
Merge pull request #2467 from prototech/ticket/12551

[ticket/12551] Float breadcrumbs to the right in RTL languages.

* prototech/ticket/12551:
  [ticket/12551] Float breadcrumbs to the right in RTL languages.
Merge pull request #2480 from rxu/ticket/12572

[ticket/12572] Fix JS error when alert message title is undefined

* rxu/ticket/12572:
  [ticket/12572] Fix JS error when alert message title is undefined
Merge pull request #2468 from nickvergessen/ticket/12555

[Ticket/12555] Make use of canonical urls to avoid duplicate content

* nickvergessen/ticket/12555:
  [ticket/12555] Add canonical URL for viewtopic
  [ticket/12555] Add canonical URL for viewforum
  [ticket/12555] Add canonical URl for memberlist mode=viewprofile
  [ticket/12555] Allow to set canonical URLs to avoid duplicate content