#87 Add support for unix sockets

[dreamcat four]

On some systems (for example in a FreeBSD jail when there is no 'localhost' loopback device), sending requests over a TCP port reduces security and creates the possibility for an insecure service to be attacked.

Implementing an alternative connection method (unix sockets) would enhance security greatly in those situations. Eliminating possibility of such insecure ports being left open to attack in misconfigured or poorly-configured systems.

Furthermore, a unix socket connection method may also help to improve performance. Depending upon the circumstances.

Please consider, thanks.

[Robert van Engelen]

Please see the documentation on how to plug-in your own socket communications, using callbacks. The engine uses BSD Unix sockets by default.