Re: issues 18, 15, 6 -- return routability

Here's a more detailed text proposal: "By default,
return routability test is done before moving the
traffic. However, [as decided in issue 18] these tests
are optional. Nodes MAY also perform these tests upon
their own initiative at other times."

This seems to cover the opinion of the folks expressed
earlier on the list, as well as your comments. Ok?

--Jari