[Spasm] Document Updates

[Jim Schaad <[e-mail]>]

I have released new versions of the two S/MIME documents to address all last
call comments received.

I have not dealt with one comment which has to do with the first default
algorithm to be used for encryption when there is no knowledge of what the
recipient of the message is capable of.  This has traditionally always been
the "best possible recommendation" that we can provide.  For this reason, I
have set it to AES-128 GCM.  

Russ has requested that this be changed to AES-256 CBC because we are
introducing not only a new algorithm but a new CMS structure at the same
time.  This means that not only would a down client be unable to decrypt the
message but would not recognize it as being an encrypted message. 

I do not really think that I care about this possible problem as it should
be dealt with cleanly, an ASN.1 decode error needs to be coped with.  For
this reason I do not think there is going to be a significant behavior
difference between an ASN.1 decode/message type recognition problem and a
cannot decrypt because the algorithm is unknown.

Jim