IPB changes

[Eddie Kohler]

I've made a couple changes in preparation for getting the IPB stuff into a
kernel.

As per Dave's suggestions, I've gotten rid of PermStrings entirely. (He was
not optimistic about PermStrings working in a downloadable module.)
Therefore, the class_name() method now has the signature

	const char *class_name() const

I've added a `conf' directory to hold .ipb files. I've checked in an
`rtm.ipb' file which should be equivalent to Robert's IP encapsulator. So
do a `cvs up -P -d' to get the new directory.

Filter now behaves slightly differently. It checks the filters from first
to last, not last to first, and sends to the first one that succeeds. There
is no warning if more than one filter would have succeeded. In the
configuration language, you can say ``-'' to mean that the filter takes any
packet, like this:

	f :: Filter(12/0a, 12/0b 13/0c, -)

That's it for now!
love,
ed