* kbx/keybox-blob.c (x509_email_kludge): Rename to ...
(_keybox_x509_email_kludge): this and make global.
* kbx/backend.h: Include ksba.h.
* kbx/backend-support.c (be_get_x509_serial): New.
(be_get_x509_keygrip): New.
* kbx/backend-sqlite.c (table_definitions): New table 'issuers'.
(run_select_statement): Implements modes ISSUER, ISSUER_SN, SUBJECT.
(store_into_userid): Add arg override_mbox.
(store_into_issuer): New.
(be_sqlite_store): Implement x509 part.