* dtable.cc (dtable::select_write): Add missing argument to debug_printf.

* fhandler.cc (fhandler_base_overlapped::setup_overlapped): Explicitly set
io_pending to false.
(fhandler_base_overlapped::has_ongoing_io): Call GetOverlappedResult to force
completion of I/O.
(fhandler_base_overlapped::wait_overlapped): Rewrite to correctly deal with
nonblocking reads and to make more race proof.
(fhandler_base_overlapped::raw_write): Deal with new enum values.
(fhandler_base_overlapped::raw_read): Ditto.  Don't deal with ongoing I/O here
since it makes no sense in the read context.
* fhandler.h (enum wait_return): Add overlapped_unknown,
overlapped_nonblocking_no_data.
* pipe.cc (pipe): Add debugging output.

winsup/cygwin/pipe.cc

@@ -378,6 +378,7 @@ pipe (int filedes[2])
       fdout = fhs[1];
       filedes[0] = fdin;
       filedes[1] = fdout;
+      debug_printf ("%d, %d", (int) fdin, (int) fdout);
     }
 
   return res;