Add gtk-sharp3 2.99.3.99
Add gtk-sharp3 2.99.3.99

Add a gtk-sharp3 package from git, versioned 2.99.3.99 to indicate it
is pre 2.99.4.

Also add patch from https://github.com/mono/gtk-sharp/pull/130 to fix
compilation on OS X.

BansheeMediaPlayer/bockbuild,BansheeMediaPlayer/bockbuild,BansheeMediaPlayer/bockbuild