Remove unused hashName declaration
Summary:
With the exception of the todo added in 2012, this function has been
untouched since 2007. It is not used anywhere else in GHC, so it appears
to be safe to remove. The accompanying comment refers to hashExpr, which
I couldn't find anywhere in the sources, either.
Test Plan: Removed declaration and export. Compiler built succesfully. No test cases exist to fail, and no other module appears to use it.
Reviewers: thomie, austin
Reviewed By: thomie, austin
Subscribers: simonmar, ezyang, carter, thomie
Differential Revision: https://phabricator.haskell.org/D261