* sigproc.h (wait_for_sigthread): Eliminate parameter.

* sigproc.cc (wait_for_sigthread): Ditto.  Don't synchronize with wait_sig
after receiving an event that it is ready to go.
(init_sig_pipe): New function.
(wait_sig): Call init_sig_pipe to create pipes for communicating signals to
this process.  Don't send sigCONT signal when initializing.
* fork.cc (frok::child): Accommodate wait_for_sigpipe parameter change.
* fhandler.h (fhandler_*::write): Make ssize_t/__stdcall.
(fhandler_*::write_overlapped): Ditto.
(fhandler_*::raw_write): Ditto.
(fhandler_*::readv): Ditto.
(fhandler_*::writev): Ditto.
(fhandler_*::raw_read): Make __stdcall.
* fhandler: Accommodate changes to read/write functions throughout.
* fhandler_clipboard.cc: Ditto.
* fhandler_console.cc: Ditto.
* fhandler_dsp.cc: Ditto.
* fhandler_fifo.cc: Ditto.
* fhandler_mailslot.cc: Ditto.
* fhandler_mem.cc: Ditto.
* fhandler_mem.cc: Ditto.
* fhandler_random.cc: Ditto.
* fhandler_tape.cc: Ditto.
* fhandler_tty.cc: Ditto.
* fhandler_virtual.cc: Ditto.
* fhandler_windows.cc: Ditto.
* fhandler_zero.cc: Ditto.
* syscalls.cc (readv): Use ssize_t as temp variable.
* fhandler.cc (fhandler_base::read): Coerce returned len to signed or it will
never be treated as < 0.
(fhandler_base::wait_overlapped): Minimize calls to GetLastError.  Remove
duplicate debugging test.  Fix error return.
* fhandler.h (fhandler_fifo::fifo_name): Declare new function.
(fhandler_fifo::close): Ditto.
(fhandler_fifo::dup): Ditto.
(fhandler_fifo::close_on_exec): Ditto.
* fhandler.cc (fhandler_fifo::fifo_name): Define new function.
(FIFO_BUF_SIZE): New define.
(cnp): Ditto.
(fhandler_fifo::open): Rework.  Use cnp to open named pipe.  Always open write
side as a client.  Open dummy client when writing and can't connect.
(wait): Rework.  Implement fifo_wait_for_next_client.  Handle signals during
connect better.  Add new fifo_wait_for_server code which polls
(sigh) waiting for server.
(fhandler_fifo::raw_read): Handle transition states when one client closes and
another is available.
(fhandler_fifo::close): Define.
(fhandler_fifo::dup): Ditto.
(fhandler_fifo::close_on_exec): Ditto.

winsup/cygwin/fhandler_zero.cc

@@ -30,7 +30,7 @@ fhandler_dev_zero::open (int flags, mode_t)
   return 1;
 }
 
-int
+ssize_t __stdcall
 fhandler_dev_zero::write (const void *, size_t len)
 {
   if (get_device () == FH_FULL)