* g10/import.c (transfer_secret_keys): Handle mode 1003.
* g10/call-agent.c (agent_import_key): Add arg mode1003.
* common/sexputil.c (make_canon_sexp): Create in secmem when the input
was in secmem.
* agent/findkey.c (agent_write_private_key): Add arg 'linkattr' and
change all callers.
* agent/command.c (cmd_import_key): Add option '--mode1003'.
Reorganize code and implement support for composite keys.