Works on Mac. Hopefully I didn't break too much on other platforms

Added some stuff to make it compile and work all nice on OSX.

Time shouldn't be a problem, changes should only affect OSX.

To let paths work properly, we had to use CoreServices. Had to add custom `QMAKE_LFLAGS` and `LIBS` settings in `LoE_PrivateServer.pro`. Hopefully it won't affect any other platforms due to that `macx {}`, but someone running on another platform should test.

To let Clang compile it properly, I had to change the way the unicode literals were represented in `convertChar`. Hopefully it shouldn't affect Windows/Linux, but please test before pulling.

I also made session key validation optional. Using the client release I am, it doesn't actually hit the login server when you join a local server, and I'm not sure how to recover the internal saltPassword it uses, so I just decided to disable session key validation in my local testing. It's set to enabled by default, so it shouldn't affect you guys.

Sorry for all the changes, but I suspect I'm using a newer or quite modified version of the client to what you guys are using (could also just be used to OSX build differences, though).