Correct @since annotations

Use parsec, drop parsec flag

- Manually generate Lexer.hs
- Temporarily disable parser-hackage-tests on appveyor (needs
  01-index.tar)
- Add root Makefile to handle commmon dev tasks (genering Lexer.hs)

cabal check flag names

Start adding a benchmark that solves for all packages on Hackage.

This benchmark is based off of a script written by @kosmikus.  It adds
functionality for running multiple trials for each package, but it is currently
missing other features.

[ci skip]

(cherry picked from commit dd57b5c7)

Fixes #4622.

[ci skip]

(cherry picked from commit ef2078d7)

Add missing separator in solver fallback message

Committed by accident as part of
45fb7929.

Without this it would print a list of packages and append
  "Trying configure anyway."
without any separator between the list and the new sentence.

[ci skip]

[ci skip]

Turn `allow-{newer,older}` into an accumulating field to match CLI semantics

[skip ci]

Refactor/cleanup of `String`/`ByteString` usage

Changelog entry:

> Change `rawSystemStdInOut` to use proper type to represent
> binary and textual data; new `Distribution.Utils.IOData` module;
> removed obsolete `startsWithBOM`, `fileHasBOM`, `fromUTF8`,
> and `toUTF8` functions; add new `toUTF8BS`/`toUTF8LBS`
> encoding functions. (#4666)

[skip ci]

This reduces the surface area of lib:Cabal by removing
entry points that Setup.hs scripts are very unlikely to
use.

Add 'store-dir' global flag for custom store location

This fixes the inconvenience occuring in `cabal.project` files of
separate `allow-*` statements overwriting each other. Currently,
without this patch,

    allow-newer: base
    allow-newer: directory

is *NOT* equivalent to

    allow-newer: base, directory

but rather to the last occurence of `allow-newer`, i.e.

    allow-newer: directory

This behaviour has been present since cabal 1.24