gpg: First working support for keyboxes.

* g10/getkey.c (get_pubkey_fast): Improve the assertion.
* kbx/keybox.h: Include iobuf.h.
* kbx/keybox-blob.c (keyboxblob_uid): Add field OFF.
(KEYBOX_WITH_OPENPGP): Remove use of this macro.
(pgp_create_key_part_single): New.
(pgp_temp_store_kid): Change to use the keybox-openpgp parser.
(pgp_create_key_part): Ditto.
(pgp_create_uid_part): Ditto.
(pgp_create_sig_part): Ditto.
(pgp_create_blob_keyblock): Ditto.
(_keybox_create_openpgp_blob): Ditto.
* kbx/keybox-search.c (keybox_get_keyblock): New.
* kbx/keybox-update.c (keybox_insert_keyblock): New.
* g10/keydb.c (parse_keyblock_image):
(keydb_get_keyblock): Support keybox.
(build_keyblock_image): New.
(keydb_insert_keyblock): Support keybox.

* kbx/kbxutil.c (import_openpgp, main): Add option --dry-run and print
a kbx file to stdout.

* kbx/keybox-file.c (_keybox_read_blob2): Allow keyblocks up to 10^6
bytes.
--

Import and key listing does now work with the keybox format.  It is
still quite slow and signature caching is completely missing.

Increasing the maximum allowed length for a keyblock was required due
to a 700k keyblock which inhibited kbxutil to list the file.
kbxutil's option name --import-openpgp is not quite appropriate
because it only creates KBX blobs from OpenPGP data.

kbx/keybox-defs.h

@@ -156,9 +156,11 @@ void _keybox_close_file (KEYBOX_HANDLE hd);
 
 
 /*-- keybox-blob.c --*/
-#ifdef KEYBOX_WITH_OPENPGP
-  /* fixme */
-#endif /*KEYBOX_WITH_OPENPGP*/
+gpg_error_t _keybox_create_openpgp_blob (KEYBOXBLOB *r_blob,
+                                         keybox_openpgp_info_t info,
+                                         const unsigned char *image,
+                                         size_t imagelen,
+                                         int as_ephemeral);
 #ifdef KEYBOX_WITH_X509
 int _keybox_create_x509_blob (KEYBOXBLOB *r_blob, ksba_cert_t cert,
                               unsigned char *sha1_digest, int as_ephemeral);