[ticket/12275] Fix a bug on the event "core.modify_username_string"

Call the event "core.modify_username_string"
also if $mode is "colour", "username" or "profile".

PHPBB3-12275
[ticket/12275] Change if (empty) to if (!isset)

PHPBB3-12275
[ticket/12531] Restore default topic link functionality in subsilver2

PHPBB3-12531
[ticket/12543] Only take over ENTER and ESC keys when alert box is active.

PHPBB3-12543
[ticket/12585] Don't check the cron on each page load

PHPBB3-12585
[ticket/12531] Add some line breaks to really long lines

PHPBB3-12531
[ticket/12585] Use a 5 minutes interval instead of 10 minutes

PHPBB3-12585
Merge pull request #2490 from Nicofuma/ticket/12585

[ticket/12585] Don't check the cron on each page load

* Nicofuma/ticket/12585:
  [ticket/12585] Use a 5 minutes interval instead of 10 minutes
  [ticket/12585] Don't check the cron on each page load
Merge pull request #2444 from VSEphpbb/ticket/12531

[ticket/12531] Restore default topic link behavior to subsilver2

* VSEphpbb/ticket/12531:
  [ticket/12531] Add some line breaks to really long lines
  [ticket/12531] Restore default topic link functionality in subsilver2
Merge pull request #2199 from Zoddo/ticket/12275

[ticket/12275] Fix a bug on the event "core.modify_username_string"

* Zoddo/ticket/12275:
  [ticket/12275] Change if (empty) to if (!isset)
  [ticket/12275] Fix a bug on the event "core.modify_username_string"
Merge pull request #2458 from prototech/ticket/12543

[ticket/12543] Only take over ENTER and ESC keys when alert box is active.

* prototech/ticket/12543:
  [ticket/12543] Only take over ENTER and ESC keys when alert box is active.