[ticket/11985] Reorganise travis/install-php-extensions.sh

PHPBB3-11985
[ticket/11985] Enable APC on command line so it can be used by PHPUnit.

PHPBB3-11985
[ticket/11985] Don't try to install APC on PHP 5.5 or higher.

PHPBB3-11985
[ticket/12159] Fix codesniffer complaints due to profilefields and passwords

The two PRs regarding profilefields and passwords manager that were recently
merged caused a few codesniffer complaints that are fixed by these changes.

PHPBB3-12159
Merge pull request #1997 from marc1706/ticket/12159

[ticket/12159] Fix codesniffer complaints due to profilefields and passwords

* marc1706/ticket/12159:
  [ticket/12159] Fix codesniffer complaints due to profilefields and passwords
[ticket/11985] Rename install -> setup. This is more generic and consistent.

PHPBB3-11985
[ticket/11985] Do not try to setup PHP extensions on HHVM.

PHPBB3-11985
[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
Merge pull request #1998 from bantu/ticket/12141

[ticket/12141] Disable opcache extension on PHP 5.5.7
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
[prep-release-3.1.0-a3] Update version to 3.1.0-a3
[prep-release-3.1.0-a3] Add migration for 3.1.0-a3
[prep-release-3.1.0-a3] Prepare Changelog
[prep-release-3.1.0-a3] Commit changelog for 3.1.0-a3