New decrypt flags GPGME_DECRYPT_LISTONLY.
* src/gpgme.h.in (GPGME_DECRYPT_LISTONLY): New. * src/decrypt.c (op_data_t): Add member list_only. (_gpgme_decrypt_status_handler): Do not return NO_DATA in list_only mode. (_gpgme_op_decrypt_init_result): Add arg flags and set the list_only flag. (_gpgme_decrypt_start): Pss flags to the init function. * src/decrypt-verify.c (decrypt_verify_start): Ditto. * src/engine-gpg.c (gpg_decrypt): Add --list-only if flag is set. * tests/run-decrypt.c (main): Add option --list-only.