Version bumped to 5.5.30 by buildsystem.
Installer [win32]: Fixed remaining issues with MariaDB.

The registry search rules should now be able to find both
mysqladmin and myisamchk. They were not found earlier due to
the registry key "Location" having been renamed "INSTALLDIR"
in the MySQL to MariaDB transition.
Installer [win32]: Mention MariaDB too where MySQL is mentioned.
Version bumped to 5.5.31 by buildsystem.