* src/gpgme.h.in (GPGME_ENCRYPT_ADD_RECP, GPGME_ENCRYPT_CHG_RECP):
New flag values.
* src/engine-gpg.c (have_cmd_modify_recipients): New.
(gpg_encrypt): Check availability of the feature and prepare command.
* tests/run-encrypt.c (main): New options --add-recipients
and --change-recipients.