wkd: New command --mirror for gpg-wks-client.

* tools/gpg-wks-client.c (aMirror,oBlacklist,oNoAutostart): New.
(opts): Add ----mirror, --no-autostart, and --blacklist.
(parse_arguments): Parse new options.
(main): Parse common.conf.  Implement aMirror.
(mirror_one_key_parm): New.
(mirror_one_keys_userid, mirror_one_key): New.
(command_mirror): New.

* tools/gpg-wks.h (struct uidinfo_list_s): Add fields flags.
* tools/wks-util.c (wks_cmd_install_key): Factor some code out to ...
(wks_install_key_core): new.

* tools/call-dirmngr.c (wkd_dirmngr_ks_get): New.
--

This implements the basic LDAP to WKD mirroring.  The blacklist
option and domain restrictions are not yet fully implemented.

Take care: In OpenLDAP you may need to increase the paged result limit
by using a configuration like:

  dn: olcDatabase={1}mdb,cn=config
  changetype: modify
  replace: olcLimits
  olcLimits: dn.subtree="dc=example,dc=org" size.prtotal=unlimited

GnuPG-bug-id: 6224

tools/call-dirmngr.h

@@ -28,5 +28,8 @@ gpg_error_t wkd_get_policy_flags (const char *addrspec, estream_t *r_buffer);
 
 gpg_error_t wkd_get_key (const char *addrspec, estream_t *r_key);
 
+gpg_error_t wkd_dirmngr_ks_get (const char *domain,
+                                gpg_error_t cb (estream_t key));
+
 
 #endif /*GNUPG_TOOLS_CALL_DIRMNGR_H*/