gpg: Avoid compiler warnings for disabled algos.

* g10/misc.c (map_cipher_openpgp_to_gcry): Add case for disabled algo.
(openpgp_pk_test_algo2): Ditto.
(map_md_openpgp_to_gcry): Ditto.
gpg: Change --print-mds to output enabled OpenPGP algos.

* g10/gpg.c (print_mds): Use opengpg_md_test_algo.  Test also for MD5
availibility.
gpg: List only available algos in --gen-key.

* g10/keygen.c (ask_algo, ask_curve): Take care of GPG_USE_<algo>.
Allow disabling of card support.

* configure.ac: Add option --disable-card-support.  Also add
am_conditional and do not build scd if card support is enabled.
Silence annoying ABI change warning.

* configure.ac [GCC]: Pass -Wno-psabi for gcc >= 4.6.  Avoid some gcc
option tests for gcc >= 4.6
--
Signed-off-by: Werner Koch <wk@gnupg.org>
(cherry picked from commit d04399a6a8b36a7fea92c304aa7309956a2e352b)

Resolved Conflicts:
	configure.ac: merged.
tests: Handle disabled algorithms.

* tests/openpgp/mds.test: Skip disabled algorithms.
* tests/openpgp/signencrypt-dsa.test: Ditto.
* tests/openpgp/sigs-dsa.test: Ditto.
gpg: Allow building without any trust model support.

* 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.
gpg: Cleanup compiler warnings due to some configure options.

* g10/photoid.c (show_photos) [DISABLE_PHOTO_VIEWER]: Mark args as
unused.
* tools/gpgconf-comp.c (my_dgettext): Mark DOMAIN as unused if NLS is
not configured.
tests: Avoid segv if dns cert lookup is not configured.

* common/dns-cert.c (get_dns_cert) [!USE_DNS_CERT]: Reset return args.
gpg: Silent more compiler warnings due to some configure options.

* g10/keygen.c (generate_keypair, gen_card_key)
(gen_card_key_with_backup) [!ENABLE_CARD_SUPPORT]: Mark unused args.