* environ.cc (struct parse_thing): Add temporary (?) "pipe_byte" option.

* globals.cc (pipe_byte): Declare.
* pipe.cc (fhandler_pipe::create): Use current process id in pipe name rather
than pid for simple name collision avoidance.  Do this only once to avoid extra
overhead when a busy pipe is found.  Honor pipe_byte to create non-message
pipes if set.
* sigproc.cc (sigproc_init): Use a specific name for the signal pipe.

winsup/cygwin/sigproc.cc

@@ -529,7 +529,7 @@ 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), NULL, 0);
+				     sizeof (sigpacket), "sigwait", 0);
   if (err)
     {
       SetLastError (err);