OSX Mavericks Support

This pull request closes #509

I'd also like to publish this to the lmms wiki if we're in agreement: 
https://github.com/tresf/lmms/wiki/Compiling-lmms-OSX

There's still much to be worked out on this platform.  I would like to start opening up individual bug reports to address each bug individually.  The build instructions in combination with these commits should make community OSX bug fixing much more feasible.

-Tres