[ticket/13051] Fix viewonline event, remove template data

PHPBB3-13051
[ticket/13051] Add a new core event to handle the template array

PHPBB3-13051
[ticket/12976] Correctly use plurals for attachment count in UCP navigation

PHPBB3-12976
[ticket/13051] Rename new event core.viewonline_modify_user_row

PHPBB3-13051
[ticket/13051] Fix core event name

PHPBB3-13051
Merge pull request #2934 from VSEphpbb/ticket/13051

[ticket/13051] Fix viewonline event (recently broken) and add a new core event
[ticket/13052] Restore timespan parameter for check_form_key()

PHPBB3-13052
Merge pull request #2939 from nickvergessen/ticket/13052

[ticket/13052] Restore timespan parameter for check_form_key()

* nickvergessen/ticket/13052:
  [ticket/13052] Restore timespan parameter for check_form_key()
[ticket/13042] Remove unused variables

PHPBB3-13042
Merge pull request #2936 from nickvergessen/ticket/12976

[ticket/12976] Correctly use plurals for attachment count in UCP navigation

* nickvergessen/ticket/12976:
  [ticket/12976] Correctly use plurals for attachment count in UCP navigation
Merge pull request #2940 from Senky/ticket/13042

[ticket/13042] Unused var in login_box()

* Senky/ticket/13042:
  [ticket/13042] Remove unused variables