Cygwin: FIFO: remember the type of the fhandler

Add data members 'reader', 'writer', and 'duplexer' to the
fhandler_fifo class.  Set them in fhandler_fifo::open.  ('duplexer'
replaces the previous '_duplexer'.)

This will be useful in later commits.

winsup/cygwin/fhandler.h

@@ -1272,7 +1272,7 @@ class fhandler_fifo: public fhandler_base
   fifo_client_handler fc_handler[MAX_CLIENTS];
   int nhandlers, nconnected;
   af_unix_spinlock_t _fifo_client_lock;
-  bool _duplexer;
+  bool reader, writer, duplexer;
   bool __reg2 wait (HANDLE);
   NTSTATUS npfs_handle (HANDLE &);
   HANDLE create_pipe_instance (bool);