Yuras authored Jan 20, 2017 and Ben Gamari committed Jan 20, 2017

Introduce a warning, -Wmissing-home-modules, to warn about home modules,
not listed in command line.

It is usefull for cabal when user fails to list a module in
`exposed-modules` and `other-modules`.

Test Plan: make TEST=MissingMod

Reviewers: mpickering, austin, bgamari

Reviewed By: bgamari

Subscribers: simonpj, mpickering, thomie

Differential Revision: https://phabricator.haskell.org/D2977

GHC Trac Issues: #13129