Allow key version number to wrap at 16 bits

We only have 16 bits on the wire for the connection key version
number, but use the number as a 32-bit quantity.  Allow all 32 bits
to be used if both endpoints can locally track that quantity.

Change-Id: I1829b1740790d33f7056711192b6cfa44a012388
Tokens SHOULD NOT expire late

jhutz wants to be explicit about it.

Change-Id: I683334cd0502fd520a9d9a5f9d16b7cc9ea4574d
Add Security Consideration for token expiry

We have only a SHOULD NOT, not a MUST NOT, but be careful if you do.

Change-Id: I74ca6db8369e3fa93874eeb1454e425e58e7922f
Normalize whitespace

Death to carriage return.

Change-Id: I52226634b841addda8db8796edd464ae9a780eaa
reorder packet handling subsections

Put the packet handling descriptions in the same
order as the levels section; clear, auth, crypt.

Change-Id: Iba20ad6eed03782da22653c2b873e2993b996d29
artwork and clarification of RXGK_AUTH packets

Add artwork to show the memory structure for calculating
the MIC and the structure that is transmitted on the wire
for for the rxgk integrity level.

Change-Id: Id2af8c63dfd6efaf8384ce5d5c443221b8b79ade
CombineTokens errors are com_err errors

Move the list of error codes to an AFS-3 registry concerns section,
and make the CombineTokens error codes com_err codes.
Keep a few examples in the body of the text, though.

Change-Id: Iee07bf65f1fe8c7a21b7435feb516570a8338364
GSSNegotiate policy errors are com_err

Either RXGK or application-specific.

Change-Id: I9f88499916f65b60e5bdf336e11f8f46979a3042