* Added OSX platform to MGSongProcessor.cs to compress mp3 songs
* MonoGame on MAC throws a notimplementedexception on IPv4Mask, so we return null on Mac Implementation. Had to add a MONOMAC define to the project.
Revert "* Added OSX platform to MGSongProcessor.cs to compress mp3 songs"

This reverts commit 642827f4c82bb9226055a69532701ad2907fdaea.
Merge pull request #1939 from WaaghMan/branch_osx3

Lidgren - MacOS issues