gpg: Print a hint on how to decrypt a non-mdc message anyway.
* g10/mainproc.c (proc_encrypted): Print a hint for legacy ciphers w/o MDC. Also print a dedicated status error code
(cherry picked from commit 874e391665405fc413a69f2ffacdb94bb08da7ff)
- Signed-off-by: Werner Koch <wk@gnupg.org>