mysql5 should be replaced_by mysql55, mysql56 or mariadb

[Jeremy Lavergne]

> The mysql51, mysql55, mysql56, mariadb and percona ports do not conflict so there are no common files, if thats what you meant.

Yup, that's basically what I meant.

> I would like MacPorts to have an [un]official default mysql port that ports can depend on or the ports can provide variants or subports for the other mysql's when desired.

Like how we handle perl? heh.