[krbdev.mit.edu #1224]ASN1 optional fields

[Ezra Peisach]

The way that the code is writen today for this sam handling
is that we send it as present - but empty.


I need to look a little more at the decoder - it may be that 
present but empty (i.e. len 0) - may have the same effect as 
not present at all. The decoder clearly anticipates that
the optional strings may not come over the wire.

	Ezra