[ticket/11716] Rename migration files and add note that it's converting a MOD

PHPBB3-11716
[ticket/12161] Do not use subdirectories in build/save directory.

This is pretty much pointless because a new build will wipe the save directory
and there are only a few files in there anyway.

PHPBB3-12161
[ticket/12141] PHP extension setup must happen before webserver + PHP-FPM.

PHPBB3-12141
[ticket/12141] Disable broken opcache extension on PHP 5.5.7.

PHPBB3-12141
[ticket/11509] Be exact when referencing the branch name.

PHPBB3-11509
[ticket/12153] Assign PAGE_NUMBER in pagination.generate_template_pagination()

PHPBB3-12153
[ticket/12153] Remove vars already assigned in generate_template_pagination().

PHPBB3-12153
[ticket/12153] Remove redundant calls to pagination.on_page().

PHPBB3-12153
[ticket/12153] Adjust pagination tests.

PHPBB3-12153
[ticket/12158] The pagination start value should be 0 when there are no items.

PHPBB3-12158
Merge pull request #1998 from bantu/ticket/12141

[ticket/12141] Disable opcache extension on PHP 5.5.7
Merge pull request #1999 from bantu/ticket/11509

[ticket/11509] Further improvements/fixes for the Travis CI commit message checker
Merge pull request #2001 from bantu/ticket/12161

[ticket/12161] Do not use subdirectories in build/save directory.
[ticket/12162] Set language to C before running diff to ensure its english

PHPBB3-12162
Merge remote-tracking branch 'github-nickvergessen/ticket/12162' into develop-olympus

* github-nickvergessen/ticket/12162:
  [ticket/12162] Set language to C before running diff to ensure its english
Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/12162] Set language to C before running diff to ensure its english
  [ticket/11509] Be exact when referencing the branch name.
  [ticket/12161] Do not use subdirectories in build/save directory.
  [ticket/11509] Run commit message checker only in one environment.
  [ticket/11509] Contrary to docs, COMMIT_RANGE is not available in PR mode.

Conflicts:
	.travis.yml
[ticket/12158] Add test data for 0 items to validate_start() test.

PHPBB3-12158
[develop] Remove left over conflict marker from merge 1a31f03
[ticket/12163] Use posts_per_page to calculate current page in viewtopic.php

PHPBB3-12163
Merge pull request #2004 from prototech/ticket/12163

[ticket/12163] Use posts_per_page to calculate current page in viewtopic.php

* prototech/ticket/12163:
  [ticket/12163] Use posts_per_page to calculate current page in viewtopic.php