gpg: Add kbnode_t for easier backporting.

* g10/gpg.h (kbnode_t): New.
gpg: Fix regression due to the keyserver import filter.

* g10/keyserver.c (keyserver_retrieval_filter): Change args.  Rewrite
to take subpakets in account.
* g10/import.c (import_one, import_secret_one): Pass keyblock to
filter.
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GnuPG-bug-id: 1680
po: Update Japanese translation.