* kbx/backend-sqlite.c (be_sqlite_rollback): New.
(be_sqlite_commit): New.
(be_sqlite_search): Take care of global transactions.
(be_sqlite_store): Ditto.
(be_sqlite_delete): Ditto.
* kbx/frontend.c (kbxd_rollback, kbxd_commit): New.
* kbx/keyboxd.h (opt): Add vars for transactions.
* kbx/kbxserver.c (struct server_local_s): Add fields next_session and
client_pid.
(session_list): New var.
(cmd_transaction): New.
(register_commands): Register command.
(kbxd_start_command_handler): Store pids and track sessions.  Do a
final rollback.