ReactiveCocoa/ReactiveCocoa — pull request #1456 by epatey (2014-08-09 00:37:47+00:00)
Title: Fix lack of thread safety in -[RACSerialDisposable disposable]

Addresses #1455

I couldn't come up with a way to do it using `OSAtomicXXX`, but I'd be happy to change it if somebody can suggest how.