mysql::dev installs developement libraries.

 Currently just has myslqclient set up as an example with the Debian OS family.

This is a proposed pattern for installing mysql development libraries.

`mysql::dev`` has a parameter for each library configured, and an `ensure` statement is passed to that parameter, i.e. `absent`, `present`, or a version string. This is checked to see if an appropriate package variable has been set in `mysql::params` by OS or OS Family. The ensure statement is then passed to the package.