Set Typeclasses Strict Resolution, close  #479

It works!  (NB: This bumps the coq submodule version, so you have to recompile coq after pulling it.)
If you can tell me why the old version doesn't work, I'd be glad to hear it.  It seems to be unable to guess that I want the `O_unit` to use the `ReflectiveSubuniverse` in the context.  Maybe it's a bug?