Move ReadP out of Cabal (to cabal-install)

- Distribution.Compat.ReadP to Distribution.Deprecated.ReadP
- Distribution.Text to Distribution.Deprecated.Text
- all Text instances needed by cabal-install to Deprecated.Text too
- Distribution.ParseUtils to Distribution.Deprecated.ParseUtils
- Remove deprecated Distribution.PrettyUtils
- new Distribution.Text with

    display = prettyShow
    simpleParse = simpleParsec

  to not break too much stuff (Custom Setup.hs)
- parseInstalledPackageInfo type signature changed to use
  `base` types

This removes around 2k lines from Cabal the library.
git diff --stat shows less, as files are moved (git is smart).
Even so, total 300 lines removal at this point.