[phobos] std.parallelism's unit tests randomly hang on win32

[David Simcha]

On 5/1/2011 8:30 PM, Sean Kelly wrote:
> Is core.atomic not saving and restoring a register it should?
>

Doesn't look like.  I've reviewed this code to check for that.  I think 
it could be one of two things:

1.  A DMD codegen bug that's not saving the registers properly.

2.  An extremely subtle concurrency bug that's causing codepaths that 
"can't happen" to be executed, meaning DMD doesn't save the registers 
properly because the relevant codepaths "can't happen".