gpg: Add push/pop found state feature to keydb.
* g10/keydb.c (keydb_handle): Add field saved_found. (keydb_new): Init new field. (keydb_push_found_state, keydb_pop_found_state): New. * g10/keyring.c (kyring_handle): Add field saved_found. (keyring_push_found_state, keyring_pop_found_state): New.
We have the same feature in gpgsm. It is very useful to check for an
unambiguous user id with a follow up update of the keyblock.
- Signed-off-by: Werner Koch <wk@gnupg.org>