[ticket/13050] Allow topic/forum subscription when email/jabber is off

Currently, there's impossible to subscribe topic/forum if emails and/or jabber
is disabled. This seems to be a 3.0 leftover since 3.1 introduces new
notification system which handles this case and offers email/jabber-free
board notifications.

PHPBB3-13050
[ticket/13026] Add template vars array to core.viewonline_overwrite_location

Add template vars array to core.viewonline_overwrite_location event
to allow modifying/adding template vars for every user row.

PHPBB3-13026
[ticket/13020] Add forum_data variable to core.viewforum_get_topic_data event

PHPBB3-13020
[ticket/13035] Remove empty meta tags

PHPBB3-13035
Merge pull request #2933 from bantu/ticket/13035

[ticket/13035] Remove empty meta tags

* bantu/ticket/13035:
  [ticket/13035] Remove empty meta tags
Merge pull request #2911 from rxu/ticket/13020

[ticket/13020] Add variables to core.viewforum_get_topic_data event
Merge pull request #2915 from rxu/ticket/13026

[ticket/13026] Add template vars array to core.viewonline_overwrite_location
[ticket/13038] Add link to number of posts of user in viewtopic

PHPBB3-13038
Merge pull request #2931 from rxu/ticket/13050

[ticket/13050] Allow topic/forum subscription when email/jabber is off

* rxu/ticket/13050:
  [ticket/13050] Allow topic/forum subscription when email/jabber is off
Merge pull request #2926 from Senky/ticket/13038

[ticket/13038] Link user post tally to their posts

* Senky/ticket/13038:
  [ticket/13038] Add link to number of posts of user in viewtopic