* 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/globals.cc

@@ -58,6 +58,7 @@ bool ignore_case_with_glob = false;
 bool dos_file_warning = true;
 bool allow_winsymlinks = false;
 bool reset_com = false; 
+bool pipe_byte = false;
 bool detect_bloda = false;
 
 bool NO_COPY in_forkee;