Add support for eapol, eap, ttls and rc4 key descriptors.
These things are used by 802.1X.

Though I may still tweak this a bit more, I think it
should already be useful to others and more or less
ready for prime time.

Some possible critisism on this version:

Maybe some of the sub-protocol names and field names
I use are a bit (too?) verbose.
The naming of fields is not entirely uniform.
The capitalization of the subprotocols as printed in the
`encapsulating' header might be a bit too much
(though dhcp/bootp capitalize too).

Right now I also `dump' the contents of ttls packets,
which may be superflous. I don't know yet what I prefer.

I'm not convinced I got the support for filtering etc. exactly right
(i.e. all fields of Proto) but what I have seems to work for me.

Nevertheless, I'm submitting this anyway because I think it is
already useful as-is, even when improvement is possible.

Axel.