Refactor freeNamesIfDecl
Refactor freeNamesIfDecl

This just switches to using pattern matching rather than field
selectors, which I generally prefer.  No change in behaviour.

ezyang/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,shlevy/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc