Comment 18 for bug 1038034

I've verified that the previous comment about the new test still holds
when the original blocking of deferrable signals is put back:
          ;; Re-increment on exit if we decremented it.
          (when (semaphore-notification-status note)
- (signal-semaphore sem)))))))
+ (signal-semaphore sem))
+ ;; KLUDGE: Prevent interrupts after this point from
+ ;; unwinding us, so that we can reason about the counts.
+ #+sb-thread
+ (sb-thread::block-deferrable-signals))))))
  ;; Create /parallel/ threads trying to acquire and then release the
  ;; semaphore. Try to asynchronously abort T2 when T1 is exiting.