like "fully trusted", "marginally trusted", etc. (get_min_ownertrust):
New. Return minimum ownertrust. (update_min_ownertrust): New. Set
minimum ownertrust. (check_regexp): New. Check a regular epression
against a user ID. (ask_ownertrust): Allow specifying a minimum value.
(get_ownertrust_info): Follow the minimum ownertrust when returning a
letter. (clear_validity): Remove minimum ownertrust when a key becomes
invalid. (release_key_items): Release regexp along with the rest of the
info. (validate_one_keyblock, validate_keys): Build a trust sig chain
while validating. Call check_regexp for regexps. Use the minimum
ownertrust if the user does not specify a genuine ownertrust.
* pkclist.c (do_edit_ownertrust): Only allow user to select a trust level
greater than the minimum value.
* parse-packet.c (can_handle_critical): Can handle critical trust and
regexp subpackets.
* trustdb.h, trustdb.c (clear_ownertrusts), delkey.c (do_delete_key),
import.c (import_one): Rename clear_ownertrust to clear_ownertrusts and
have it clear the min_ownertrust value as well.
* keylist.c (list_keyblock_print): Indent uid to match pub and sig.
