Ben Gamari authored Dec 14, 2015 and Ben Gamari committed Dec 14, 2015

Summary:
Deriving clauses in the TH representations of data, newtype, data
instance, and newtype instance declarations previously were just [Name],
which didn't allow for more complex derived classes, eg. multi-parameter
typeclasses.

This switches out [Name] for Cxt, representing the derived classes as
types instead of names.

Test Plan: validate

Reviewers: goldfire, spinda, austin

Reviewed By: goldfire, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1202

GHC Trac Issues: #10819