mono/mono — pull request #850 by ranma42 (2013-12-31 15:10:53+00:00)
Title: Use LIFO policy for CancellationTokenSource

The .NET implementation of CancellationTokenSource invokes the
callbacks in the opposite order from that of the registration.
In order to mixamize compatibility, use the same order.

Fixes https://bugzilla.xamarin.com/show_bug.cgi?id=16992