[ticket/12540] Fix broken placeholders in language files

PHPBB3-12540
Merge pull request #2454 from nickvergessen/ticket/12540

[ticket/12540] Fix broken placeholders in language files

* nickvergessen/ticket/12540:
  [ticket/12540] Fix broken placeholders in language files
Merge branch 'develop-olympus' into develop-ascraeus

* develop-olympus:
  [ticket/12540] Fix broken placeholders in language files

Conflicts:
	phpBB/language/en/common.php
	phpBB/language/en/posting.php
	phpBB/language/en/ucp.php
[ticket/12433] Use a different message when nesting of quotes is not allowed

PHPBB3-12433
[ticket/11163] Add ext/index.htm

PHPBB3-11163
Merge pull request #2464 from nickvergessen/ticket/11163

[ticket/11163] Add ext/index.htm

* nickvergessen/ticket/11163:
  [ticket/11163] Add ext/index.htm
Merge pull request #2463 from nickvergessen/ticket/12433

[ticket/12433] Use a different message when nesting of quotes is not allowed

* nickvergessen/ticket/12433:
  [ticket/12433] Use a different message when nesting of quotes is not allowed