Updates for MariaDB 10.
Very untested MariaDB 10 series.

Package-Manager: portage-2.2.0_alpha166
Update virtual for MariaDB, but perhaps it should be in virtual/mysql-5.6.

Package-Manager: portage-2.2.0_alpha166
Remove extra src_prepare from MariaDB 5.5.x for bug 462078
Cleanup IUSE="berkdb" and EAPI support.
Drop EAPI 3 as we are now using REQUIRED_USE and all builds are EAPI4+ which use mysql-v2.eclass.
Drop IUSE="berkdb" as only a post-install note affected <5.1 and mysql-v2.eclass only supports 5.1.50+