* src/gpgme.h.in (gpgme_encrypt_flags_t): New flag
GPGME_ENCRYPT_SYMMETRIC.
* src/engine-gpg.c (gpg_encrypt): Also add --symmetric if the flag
is given.
* NEWS: Mention new flag.
* tests/run-encrypt.c (show_usage): Extend for --symmetric.
(main): Handle --symmetric.
(main): Set passphrase_cb in loopback mode.
(main): Fix encrypt call if no recipients are given.
* tests/gpg/t-encrypt-mixed.c: New.
* tests/gpg/Makefile.am (c_tests): Add new test.
* doc/gpgme.texi: Document new flag.
