Util: Add interface detection for FreeBSD (bug 1730)

I've also been hit with this bug on FreeBSD where
iproute2 is not available.

FreeBSD 8.2-STABLE i386

I wrote a little patch to make gpodder work on FreeBSD.
Add an extension that displays download progress in the windows taskbar
Merge branch 'master' of http://github.com/gpodder/gpodder
Merge http://github.com/smunkel/gpodder