* fhandler.h (fhandler_fifo::arm): Declare new function.

* fhandler_fifo.cc (fhandler_fifo::arm): Define new function.
(fhandler_fifo::open): Fix handling of RDWR pipes to avoid opening a second
handle.  Use arm() function to set events.
(fhandler_fifo::raw_read): Correctly go into "connect again logic" when we
detect another writer is available.  Use arm() function to set event.
* pipe.cc (fhandler_pipe::create): Add more detail to debugging output.

winsup/cygwin/fhandler.h

@@ -738,6 +738,7 @@ public:
   bool isfifo () const { return true; }
   void set_close_on_exec (bool val);
   void __stdcall raw_read (void *ptr, size_t& ulen) __attribute__ ((regparm (3)));
+  bool arm (HANDLE h);
   void fixup_after_fork (HANDLE);
   int __stdcall fstatvfs (struct statvfs *buf) __attribute__ ((regparm (2)));
   select_record *select_read (select_stuff *);