Now, for example, when having equiv (Some x) (Some y) it will
try to find a Proper whose range is an equiv before hitting the
eq instance. My hack is general enough that it works for Forall2,
dist, and so on, too.

Initial commit by Amin Timany.

This seems to shorten type class search.

Also, slightly reorganize.

Thanks to Amin Timany for the suggestion.