Libjingle for Mac OS X

As Kev announced earlier today, we took the dust of our Libjingle branch of Psi, and merged it into the mainline development branch (mainly to ease code management). It is not unusual to discover things when you go through stuff you haven’t seen in a while, and this time was no different: we found out, much to our surprise, that we actually had a working support for Libjingle on Mac OS X all this time!