Make MonoMac_Disposer entirely static to avoid race conditions at shutdown.
Make MonoMac_Disposer entirely static to avoid race conditions at shutdown.

Otherwise we might try to re-create the disposer instance after the GC had
freed it: https://gist.github.com/e36c45d069d26bc5c5f8

Also ensure the super handle is freed exactly once.

dlech/monomac,PlayScriptRedux/monomac