removed system-getifaddrs dependency

[jaroszan]

Modified version, now local_hostname is accepted. Still 2 issues are present:

1. Double INVITE sent on Windows 7
2. When local_hostname is specifed sending side gets proper local_hostname in Contact header, while receiving side inserts local IP.

[jaroszan]

I noticed that double INVITE does not necessarily pop up each time on Windows, but still in the majority of the cases. It doesn't depend whether sending side is quaff or real application.

[rkday]

Sorry for the delay on this, @jaroszan ! I'm about to start working on Quaff again, and this looks like a good fix - although it would be good if you could remove the quaff-0.8.0.gem file as I don't think this should be checked in.

One thing I wanted to flag is that I'm planning to switch Quaff from being GPL-licensed to being dual-licensed under the GPL or MIT. Are you happy for your changes to be dual-licensed like that? (If not, I'm happy to back out 6a35b15 so that I'm not distributing any of your code under the MIT license.)

[jaroszan]

Removed gem file, it was accidentally committed. Please check if it's ok now.