Fixes U4-2187 - Enable support for MySQL on Linux

This pull request is migrated from the patch supplied in http://issues.umbraco.org/issue/U4-2187

It allows Umbraco to be installed with a connection to a MySQL server running on Linux.

It is very simple and works on our production website but as @nul800sebastiaan mentions at the end of the issue comments, it is not possible to replicate the problem (and test this fix) with a Windows installation of MySQL.

Thanks,
Chris