* configure.ac: Add option --disable-trust-models
(NO_TRUST_MODELS): New ac_define and am_conditional.
* g10/Makefile.am (trust_source): New.
(gpg2_SOURCES): Factor some files out to above. Add trust.c.
* g10/gpg.c [NO_TRUST_MODELS]: Disable options --export-ownertrust,
--import-ownertrust, --update-trustdb, --check-trustdb, --fix-trustdb,
--list-trustdb, --trustdb-name, --auto-check-trustdb,
--no-auto-check-trustdb, and --force-ownertrust.
(parse_trust_model) [NO_TRUST_MODELS]: Do not build.
(main) [NO_TRUST_MODELS]: Set trust_model to always and exclude all
trustdb related option code.
* g10/keyedit.c (cmds) [NO_TRUST_MODELS]: Remove menu items "trust",
"enable", and "disable".
* g10/keylist.c (public_key_list) [NO_TRUST_MODELS]: Do not print
"tru" record.
* g10/trust.c: New.
* g10/trustdb.c (struct key_item): Move to trustdb.h.
(register_trusted_keyid): Rename to tdb_register_trusted_keyid.
(register_trusted_key): Rename to tdb_register_trusted_key.
(trust_letter, uid_trust_string_fixed, trust_value_to_string)
(string_to_trust_value, get_ownertrust_with_min, get_ownertrust_info)
(get_ownertrust_string, get_validity_info, get_validity_string)
(clean_sigs_from_uid, clean_uid_from_key, clean_key): Move to trust.c.
(mark_usable_uid_certs): Move to trust.c and make global.
(is_in_klist): Move as inline to trustdb.h.
(trustdb_check_or_update): Rename to tdb_check_or_update
(revalidation_mark): Rename to tdb_revalidation_mark.
(get_ownertrust): Rename to tdb_get_ownertrust.
(get_min_ownertrust): Rename to tdb_get_min_ownertrust.
(update_ownertrust): Rename to tdb_update_ownertrust.
(clear_ownertrusts): Rename to tdb_clear_ownertrusts.
(cache_disabled_value): Rename to tdb_cache_disabled_value.
(check_trustdb_stale): Rename to tdb_check_trustdb_stale.
(get_validity): Rename to tdb_get_validity_core, add arg MAIN_PK and
factor some code out to ...
* trust.c (get_validity): ...new.
(check_or_update_trustdb): New wrapper.
(revalidation_mark): New wrapper.
(get_ownertrust): New wrapper.
(get_ownertrust_with_min): New wrapper.
(update_ownertrust): New wrapper.
(clear_ownertrusts): New wrapper.
(cache_disabled_value): New wrapper.
(check_trustdb_stale): New wrapper.
* tests/openpgp/defs.inc (opt_always): New. Use in all tests instead
of --always-trust.
