Platform testing for concurrency scheduler runloop

[Allison Randal]

I'm about to turn on the concurrency scheduler runloop in Parrot trunk. 
Before I do, I'd like test results on as many platforms as possible 
(especially Windows, since it doesn't use POSIX threads).

To test it, edit src/inter_create.c and uncomment the two lines that 
start with 'Parrot_cx...". Then run 'make test' and let me know if it 
fails any tests that passed before.

Thanks,
Allison