Checklist for submitted patches

This is the beginning of a checklist to check for patches submitted for merge.

• Includes regression test?

• Does patch add a user-visible command-line flag?

  • Document in users guide (docs/users_guide) and utils/mkUserGuidePart/Options/

• Does patch change a core library (e.g. base)?

  • Has the Core Libraries Committee approved?
  • Document change in migration guide on Wiki
  • Document change in the library's changelog
  • Document change in the users guide release notes

• Introduces new syntax?

  • Document in docs/users_guide/glasgow_exts.rst
  • Document in docs/users_guide/*-relnotes.rst
  • Add Template Haskell support

• Builds with last two releases of GHC?