* pgg-pgp5.el (lookup-key-string): Use `call-process' instead of

* pgg-pgp5.el (lookup-key-string): Use `call-process' instead of
`pgg-pgp5-process-region'.
(encrypt-region): Use `pgg-process-when-success'; if the output
buffer is empty, don't copy errors, just return nil.
(decrypt-region): Likewise.
(verify-region): Likewise.
(sign-region): Accept optional argument `clearsign'.