Work with MySQL Sockets

This passes anything that is not a valid port (0<int<65535) as a unix socket.
I tested this with unix sockets; this needs to be tested with a non-standard mysql port as well but I don't foresee any issues.

To use a unix socket, even one different than PHP's mysql.default_socket..
* Database Host = localhost:/path/to/socket
The port variable is no longe required. Inline the `ctype_digit($socket) && $socket<=65535` here?