Accept the protocol parameter as specified in the security multiparts
document.
Since the parameter is useful in some cases, it's probably better to keep it.
I really would like to see the multipart/signed type extended to allow multiple
signature parts (an implicit multipart/alt-sig). The current protocol param
prevents it, but a workaround is to make that param into a list...
But since this change would be "upward compatible" in the sense that it's a
strict
extension of the current proposal, it's a non issue (for now). It's better to
have something out *now* as long as it can be easily extended later if
necessary !
Stefan