We can extend in the future as necessary. thc wasn't written for
our platform directory layout, and it's not worth ripping it apart
right now.

Also, reverted old changes back (uncommented asserts, etc.).

fixed stack overflow bug in ASYNC. This is a bug in Barrelfish. The RETURN_CONT macro was not popping the return address off of the stack when it should have. This would only happen when ASYNC was called a lot without anything yielding within it. I think this is why the bug was undiscovered.