On mach, allow other ruby green threads to continue during semaphore wait
On mach, allow other ruby threads to continue during semaphore try_wait
On posix, allow ruby threads to continue during wait / try_wait
Moved tests to just semaphore, and fixed thread joining
Workaround apparent bug in 1.8.7/REE: block all during sem_timedwait
Disable test on 1.8.7, since workaround is to allow blocking on that version
Merge pull request #5 from ms-ati/allow-ruby-threads-to-continue

Fix: Allow ruby green threads to continue while waiting on semaphore