* src/w32-io.c (hddesc_t): New.
(reader_context_s, writer_context_s): Replace file_sock and file_hd by
the hddesc_t hdd.
(fd_table): Ditto.  Add want_reader and want_writer.
(hddesc_lock): New lock variable.
(new_hddesc, ref_hddesc): New.
(release_hddesc): New.
(reader, writer): Call release_hddesc.
(create_reader, create_writer): Change for new hddesc scheme.
(destroy_reader, destroy_writer): Replace closing by a call to
release_hddesc.
(_gpgme_io_pipe): Change for new hddesc scheme.
(_gpgme_io_close): Ditto.
(_gpgme_io_dup): Ditto.  Use want_reader and want_writer.
(_gpgme_io_socket): Change for new hddesc scheme.