coap-misc version that addresses #241

I have just submitted a new version of coap-misc that contains an attempt to address #241 (enabling
protocol evolution in the presence of proxies, section 7).
I believe that is the last really big problem we need to solve.
Unfortunately, it also causes one big, breaking change: renumbering all options.
(It also gets rid of fenceposts, which become a bit untenable with the more complex numbering scheme.
It works together with the longjumps that have been proposed in coap-misc-19 already to solve #214, which
have been updated for this, too, section 3.2.1.)

Htmlized:        http://tools.ietf.org/html/draft-bormann-coap-misc-20
Diff:            http://www.ietf.org/rfcdiff?url2=draft-bormann-coap-misc-20

We will need some time tomorrow to decide whether we need to solve this problem, and which solution is right.

Grüße, Carsten