Drush: Upgrade and set default command line version to mini-7-21-12-2014
Sync to 2.4.x
Init BOA-2.4.0-dev
PHP compiled with --with-curlwrappers will cause issues with HTTP authentication and GitHub.
PHP: Force rebuild to remove --with-curlwrappers if detected and not defined in _PHP_EXTRA_CONF
Drush 7 requires composer.
Force PHP rebuild properly.
Use mirror to download complete vendor directory for Drush 7.

Required to avoid GitHub API rate limit breaking installation with composer.
PHP: Make sure that --with-curlwrappers defined via _PHP_EXTRA_CONF is ignored for 5.5
Drush: Upgrade and set default command line version to mini-7-22-12-2014
MariaDB 5.5.41
Sync Drush versions tested.
Sync naming convention.
PHP: Always install and use by default version 5.5

PHP 5.3 is no longer supported and shouldn't be used in production. We are switching to use PHP 5.5 by default, and it must be always installed, even if not specified in _PHP_MULTI_INSTALL, because it is used as a fallback option when PHP version is incorrectly specified in config files for any reason.
PHP: OPcache configuration for Drupal 8 - Fixes #419