gpg: New option --no-symkey-cache.
* g10/gpg.c (oNoSymkeyCache): New. (opts): Add that option. (main): Set var. * g10/options.h (struct opt): New field no_symkey_cache. * g10/passphrase.c (passphrase_to_dek): Implement that feature.
- Signed-off-by: Werner Koch <wk@gnupg.org>