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

PHPBB3-13038
[ticket/13038] Use already existing template variable

PHPBB3-13038
[ticket/13038] Return viewtopic.php to original state

PHPBB3-13038
[ticket/13038] Show link only if permission granted

PHPBB3-13038
Merge pull request #2926 from Senky/ticket/13038

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

* Senky/ticket/13038:
  [ticket/13038] Show link only if permission granted
  [ticket/13038] Return viewtopic.php to original state
  [ticket/13038] Use already existing template variable
  [ticket/13038] Add link to number of posts of user in viewtopic