Faking the version string only works with MariaDB-Clients

Changing the server version string only works with MariaDB clients.

Problem is that only these know to remove the RPL_VERSION_HACK prefix ("5.5.5-") added by the server, and that the server even applies the RPL_VERSION_HACK prefix if the version string was explicitly set to a different value in my.cnf

How to reproduce:

• change version to a different string in my.cnf, e.g.

  version=5.6.23-log"

• connect to server with mysql client binary from MariaDB distribution:

  Welcome to the MariaDB monitor. Commands end with ; or \g.

  Your MySQL connection id is 6

  Server version: 5.6.23-log Source distribution

• connect to server with mysql client binary from MySQL distribution:

  Welcome to the MySQL monitor. Commands end with ; or \g.

  Your MySQL connection id is 7

  Server version: 5.5.5-5.6.23-log Source distribution

This leads to e.g. JDBC reporting a major and minor server version of 5 each, no matter what "version" is actually set to, so defeating the main purpose of version being fakable ...