[ticket/11920] Add MariaDB environment to Travis-CI.

PHPBB3-11920
[ticket/11920] Have to use empty root password otherwise db creation fails.

PHPBB3-11920
[ticket/11921] Improve appearance of Notifications in linklist

PHPBB3-11921
[ticket/11921] Improve appearance of PM notifications in linklist

PHPBB3-11921
Merge pull request #1780 from bantu/ticket/11920

[ticket/11920] Add MariaDB environment to Travis-CI.
Merge remote-tracking branch 'github-phpbb/develop-olympus' into develop

* github-phpbb/develop-olympus:
  [ticket/11920] Have to use empty root password otherwise db creation fails.
  [ticket/11920] Add MariaDB environment to Travis-CI.

Conflicts:
	.travis.yml
[ticket/11920] Actually call travis/setup-mariadb.sh.

PHPBB3-11920
[develop] Update version to 3.1.0-a2-dev
[ticket/11921] Remove "l_" from non-lang variables

PHPBB3-11921
[ticket/11926] Fix plupload migration dependency.

PHPBB3-11926
Merge pull request #1783 from bantu/ticket/11926

[ticket/11926] Fix plupload migration dependency.
[ticket/11920] Manually purge mysql-common.

PHPBB3-11920
[ticket/11920] Print MariaDB version after successful setup.

PHPBB3-11920
Merge pull request #1782 from bantu/ticket/11920

[ticket/11920] Actually call travis/setup-mariadb.sh.
Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/11920] Print MariaDB version after successful setup.
  [ticket/11920] Manually purge mysql-common.
  [ticket/11920] Actually call travis/setup-mariadb.sh.
[ticket/11921] Move any HTML for Notifications to the templates
PHPBB3-11921
[ticket/11921] Only get the count of unread PMs
PHPBB3-11921
[ticket/11921] Directly inject unread messages count into the template

PHPBB3-11921
Merge pull request #1781 from VSEphpbb/ticket/11921

Ticket/11921 - Streamline PMs and Notifications in Header Link List
[ticket/10948] Separate color swatch cells.

PHPBB3-10948