* fhandler.cc (fhandler_base::read): Return just read ahead characters if slow

device.
* fhandler.h (fhandler_base::set_eof): New virtual method.
(fhandler_pipe::set_eof): New method.
* pipe.cc (fhandler_pipe::fhandler_pipe): Clear saweof flag.
(fhandler_pipe::read): Return immediately if hit eof.
(fhandler_pipe::hit_eof): Return true if saweof flag is set.
* select.cc (peek_pipe): Don't call PeekNamedPipe if we couldn't grab the guard
mutex.

winsup/cygwin/fhandler.cc

@@ -479,6 +479,9 @@ fhandler_base::read (void *in_ptr, size_t in_len)
 	len--;
       }
 
+  if (copied_chars && is_slow ())
+    return copied_chars;
+
   if (len)
     {
       int readlen = raw_read (ptr + copied_chars, len);