Fixing the MachO (DARWIN) build, which broke when wtc checked in a patch in bug 153525. r=bryner.

nsprpub/pr/src/pthreads/ptthread.c

@@ -1220,7 +1220,7 @@ static void suspend_signal_handler(PRIntn sig)
 	while (me->suspend & PT_THREAD_SUSPENDED)
 	{
 #if !defined(FREEBSD) && !defined(NETBSD) && !defined(OPENBSD) \
-    && !defined(BSDI) && !defined(VMS) && !defined(UNIXWARE)  /*XXX*/
+    && !defined(BSDI) && !defined(VMS) && !defined(UNIXWARE) && !defined(DARWIN)  /*XXX*/
         PRIntn rv;
 	    sigwait(&sigwait_set, &rv);
 #endif