Replace HsBang type with HsSrcBang and HsImplBang

Authored by adamse.

Description

Replace HsBang type with HsSrcBang and HsImplBang

Updates haddock submodule.

Reviewers: tibbe, goldfire, simonpj, austin, bgamari

Reviewed By: simonpj, bgamari

Subscribers: goldfire, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D1069