* dir.cc (dirfd): Per POSIX, return EINVAL on invalid directory stream.

(telldir): Per POSIX, return -1 and set errno to EBADF, rather than
	just returning 0, on invalid directory stream.
	* signal.cc (sigwaitinfo): Return -1, not EFAULT, when SEGV was catched.

winsup/cygwin/signal.cc

@@ -564,7 +564,7 @@ sigwaitinfo (const sigset_t *set, siginfo_t *info)
 
   myfault efault;
   if (efault.faulted (EFAULT))
-    return EFAULT;
+    return -1;
 
   set_signal_mask (_my_tls.sigwait_mask, *set);
   sig_dispatch_pending (true);