the entire ISIS header into a structure - that way, if we run out of
packet data in the middle of the header, we at least dissect the stuff
for which we have packet data.
svn path=/trunk/; revision=3629
and have dissectors for protocols that run at the OSI network layer
register themselves with it using "dissector_add()".
Make various dissectors static if they can be, and remove from header
files declarations of those dissectors.
svn path=/trunk/; revision=1873