Adam Gundry authored Nov 26, 2015 and Ben Gamari committed Nov 26, 2015

This is a first draft of the user manual documentation for
DuplicateRecordFields. Feedback welcome. I've intentionally made this a
minimal change, but I wonder if it might make sense to pull out all the
subsections on record system extensions ("Traditional record syntax",
and "Record field disambiguation" through to "Record wildcards") into a
new section? That is, is it worth breaking down the rather monolithic
"Syntactic extensions" section?

Test Plan: n/a

Reviewers: simonpj, bgamari, austin

Reviewed By: bgamari, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1522