SMB sharing on Mac OS X hosts

For I project I'm working on I'm trying to make SMB sharing work on **OS X hosts**.

Before possibly create an external plugin I've tried to integrate my work into core, just in case it could be of your interest.

I've also successfully tested the patch against #4209, so even the combination **OS X host** -> **Win guest** should work.

I've used OS X 10.8 for tests, theoretically the code should also work on 10.9. For sure it **doesn't work** on 10.7 and lower, since it relies on the `sharing` command introduced with 10.8

Feel free to catch me for any need. I never told you "thank you" for this awesome piece of software? :smile: