dirmngr: Return modifyTimestamp and add server option --newer.
* dirmngr/server.c (cmd_ks_get): Add option --newer. (cmd_ad_query): Ditto. * dirmngr/ldap-misc.c (isotime2rfc4517): New. (rfc4517toisotime): New. * dirmngr/ks-action.c (ks_action_get): Add arg newer and pass on. (ks_action_query): Ditto. * dirmngr/ks-engine-ldap.c (extract_keys): Print new "chg" record. (ks_ldap_get): Add arg newer. Modify filter with newer arg. (ks_ldap_search): Print the modifyTimestamp. (ks_ldap_query): Add arg newer. Modify filter with newer arg.
Note that the modifyTimestamp is also available on Windows, where its
value is more commonly known as whenChanged. Both are constructed
attributes.
Note that the --newer option is a bit of a misnomer because LDAP has
only a greater-or-equal and no greater-than operator.
(cherry picked from commit 56d309133f0e54ac5e2f95871fb74f8cb97e2636)