niteria authored Jul 17, 2015 and Simon Marlow committed Jul 17, 2015

Summary:
Before this change the `RULES` would be attached to one for the names from
the module that appear on the left hand side. The choice depended on the
`uniq` that was generated, which are known to be non-deterministic (a
separate, bigger problem). Now we use `OccName`s which should be stable.

Analogously for instance declarations, but they are attached to one of
the types involved.

Test Plan:
contbuild
it made `Data.Text.Internal.Fusion.Common` interface stable, previously
stream fusion rule would be attached either to `streamList` or
`unstreamList` depending on if the module was compiled after `cabal
clean` or after `find | grep '\.o$' | xargs rm`.

Reviewers: simonpj, austin, bgamari, simonmar

Subscribers: puffnfresh, thomie

Differential Revision: https://phabricator.haskell.org/D1073

GHC Trac Issues: #4012