niteria authored Apr 18, 2016 and Ben Gamari committed Apr 18, 2016

The version of `haddock` that ghc has as a submodule has an option
for generating linkified sources. I don't think it hurts to have this
and they are great for exploring the codebase.

I'd be nice if harbormaster or travis published them somewhere, but
I don't know how to do that yet.

Test Plan:
uncomment, run `make` and look at the
nicely linkified sources in `compiler/stage2/doc/html/ghc/`

Reviewers: hvr, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie, simonmar

Differential Revision: https://phabricator.haskell.org/D2119

(cherry picked from commit 3dac53fa)