Alex Crichton 8fcf62b638 Don't abort if the runtime is run twice.
This changes an `assert_once_ever!` assertion to just a plain old assertion
around an atomic boolean to ensure that one particular runtime doesn't attempt
to exit twice.

Closes #9739
2013-10-09 12:38:18 -07:00
..
2013-10-03 00:15:54 -07:00