Summary:
There has been at least one breaking change to
`template-haskell` (the removal of `qAddForeignFile`) which is
causing packages like `th-orphans` and `singletons` to fail to build
with GHC HEAD. Let's bump `template-haskell`'s major version number
so that these packages can properly guard against these changes.

While I was in town, I also started a `changelog` section for
the next major version of `template-haskell`, and copied over
finishing touches for `template-haskell-2.13.0.0`.

Test Plan: ./validate

Reviewers: bgamari

Reviewed By: bgamari

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D4558