* fhandler.h (PIPE_ADD_PID): Define new flag.

* pipe.cc (fhandler_pipe::create): Don't indiscriminately add process id to
every pipe since some pipe names (fifo, tty) don't need it.
* sigproc.cc (sigproc_init): Pass PIPE_ADD_PID to fhandler_pipe::create to
ensure that pid is always part of sigwait pipe name.

winsup/cygwin/sigproc.cc

@@ -529,7 +529,8 @@ sigproc_init ()
   char char_sa_buf[1024];
   PSECURITY_ATTRIBUTES sa = sec_user_nih ((PSECURITY_ATTRIBUTES) char_sa_buf, cygheap->user.sid());
   DWORD err = fhandler_pipe::create (sa, &my_readsig, &my_sendsig,
-				     sizeof (sigpacket), "sigwait", 0);
+				     sizeof (sigpacket), "sigwait",
+				     PIPE_ADD_PID);
   if (err)
     {
       SetLastError (err);