* src/engine-gpg.c (gpg_encrypt_sign): Set use_gpgtar engine flag if
GPGME_ENCRYPT_ARCHIVE mode is set. Check for new enough gpg. Use
add_gpg_arg_with_value for gpg-only options with a value and
add_gpg_arg for gpg-only options without a value. Set extra options for
gpgtar and pass input data to stdin when using gpgtar.
* tests/run-encrypt.c (print_result): Rename to print_encrypt_result.
Print header.
(print_sign_result): New.
(show_usage): New option --sign.
(main): Parse new option. Sign and encrypt --sign is given.
Print results of signing additionally to results of encryption.