Save renamed syntax when signature merging.

Authored by ezyang on Mar 13 2017, 4:22 AM.

Description

Save renamed syntax when signature merging.

Summary:
This is required to make Haddock work correctly.

Comes with a Haddock submodule update for better rendering.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: bgamari, austin

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3335