* g10/gpg.c (exportSecretSshKey): New.
(opts): Add --export-secret-ssh-key.
(main): Implement option.
* g10/export.c (do_export_stream): Factor keywrap key code out to ...
(get_keywrap_key): new.
(mb_write_uint32, mb_write_uint8)
(mb_write_data, mb_write_cstring)
(mb_write_string, mb_write_mpi): New.
(receive_raw_seckey_from_agent): New.
(export_secret_ssh_key): New.