* fhandler.cc (fhandler_base::is_nonblocking): New method.

(fhandler_base::set_nonblocking): Ditto.
        * fhandler.h (fhandler_base): Declare new methods `is_nonblocking' and
        `set_nonblocking'.
        * fhandler_socket.cc (fhandler_socket::ioctl): Use `set_nonblocking'.
        * fhandler_tty.cc (fhandler_pty_master::process_slave_output):
        Use `is_nonblocking'.
        (fhandler_tty_slave::read): Ditto.
        (fhandler_tty_slave::ioctl): Use `set_nonblocking'.
        (fhandler_pty_master::ioctl): Ditto.
        * net.cc (cygwin_sendto): Fallback to winsock 1 functionality
        in case of nonblocking IO.
        (cygwin_recvfrom): Ditto.
        (cygwin_recv): Ditto.
        (cygwin_send): Ditto.
        * syscalls.cc (_read): Use `is_nonblocking'.

winsup/cygwin/fhandler.h

@@ -207,6 +207,9 @@ public:
   int get_flags () { return openflags; }
   void set_flags (int x) { openflags = x; }
 
+  int is_nonblocking ();
+  void set_nonblocking (int yes);
+
   int get_w_binary () { return FHISSETF (WBINARY); }
   int get_r_binary () { return FHISSETF (RBINARY); }