Fixes #7.

* The patches for `asn1-encoding`, `control-monad-omega`,
  `equivalence`, `hedgehog`, `language-c`, `socks`, `streaming`,
  `turtle`, and `vector-th-unbox` are no longer needed, as the latest
  Hackage versions support GHC 8.8 and HEAD.
* The patches for `regex-pcre-builtin`, `safecopy`,
  `skylighting-core`, and `texmath` have been migrated to the latest
  Hackage versions.
* A patch for `vinyl-0.12.0` has been added. This is mostly the same
  as the patch for `vinyl-0.11.0`, except that fewer changes are
  needed, since `vinyl-0.12.0` supports GHC 8.8.

* Update `language-haskell-extract` to build against
  `template-haskell-2.16.*`.
* Update `lens` so that its doctests pass on GHC 8.10.
  See ghc#16876.

Adds a workaround for
#6 by fetching sources
individually.

* Add a patch for `Cabal-2.4.1.0`. While this is not the most recent
  release of `Cabal`, it still appears in many build plans, so it is
  useful to patch.
* Migrate the `yesod-core` patch to the latest Hackage release.

The patches for `haskell-src-meta`, `inspection-testing`, and
`shakespeare` need to be migrated to the latest Hackage releases.

The patches for `happy`, `haskell-src-exts`, `kind-generics`,
`kind-generics-th`, and `xml-hamlet` all have newer versions on
Hackage that build with GHC 8.8 and HEAD, so drop them.

* Update the patches for `cassava`, `hpack`, and `yesod-core` to the
  latest Hackage releases.
* Drop the `attoparsec` and `shelly` patches, as the latest Hackage
  releases support GHC 8.8.1 and HEAD.

* `barbies` must adapt to GHC proposal 103
  (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0103-no-kind-vars.rst),
  which has been implemented in 8.9.
* `inspection-testing` must adapt to changes in the GHC API.
* `shakespeare` and `yesod-core` must adapt to the type of `TupE`
  changing in `template-haskell-2.16.0.0`.

* Migrate the patches for `doctest`, `free`, `persistent`, and `yesod-core`
  to the latest versions on Hackage.
* Remove the patches for `Cabal`, `bytes`, `cabal-doctest`, `ghc-paths`,
  `hsc2hs`, `polyparse`, `singleton-nats`, `tar`, `yaml`, and `zlib`, as
  more recent versions of these packages (that support GHC 8.8 and HEAD)
  are now available on Hackage.

I opted not to remove the `th-desugar-1.9`/`singletons-2.5.1` patches for
now, even though they are not the latest Hackage releases, since upgrading
them can be a nontrivial process (similar to the `primitive-0.6`/`-0.7`
situation).

I accidentally dropped this in
0a89f945. Oops.

This is needed to allow `doctest` to build with GHC HEAD afer commit
ghc@bfccd832.

* The patches for `cborg`, `dlist`, and `th-data-compat` were
  removed, since they now have newer versions on Hackage that build
  with GHC HEAD.
* Additional Hackage revisions for `attoparsec`, `cassava`,
  `hackage-security`, `hedgehog`, `lens`, `streaming`, and `turtle`
  are now on Hackage, so update their checked-in `.cabal` files
  (or if their `.cabal` files haven't been checked in yet, as is
  the case for `streaming`, and `turtle`, check them in now).

This fixes #2 by tweaking `scripts/head.hackage` in two ways:

1. This changes the script to use
   `cabal new-update head.hackage.ghc.haskell.org`, not
   `cabal new-update head.hackage`, since the former is now the name
   of the `repository`. Since `head.hackage.ghc.haskell.org` is
   referred to in quite a few places in the script, I factored this
   out into its own variable.
2. This changes the `url` to use `http://`, not `https://`, so that
   `http-transport: plain-http` works properly. An alternative would
   be to keep the use of `https://` and use `http-transport: curl`
   instead, but that assumes the existence of a `curl` binary on
   one's machine, making it a less portable solution. In any case,
   the use of `http://` in this script shouldn't pose any security
   issues, since `hackage-security` already introduces a security
   layer independent of CAs.

- v2-update is preferred (i.e. `v2-` prefix)
- but it's actually broken, due still existing `cabal-install` bug in
  non-append repository updates
- Also add explicit link to haskell.gitlab.com

Patch libraries to work with GHC 8.9

See merge request ghc/head.hackage!8

Add sop-core-0.5.0.0 patch

See merge request ghc/head.hackage!7

nix: Rip out brokenPackages

See merge request ghc/head.hackage!6

Test all packages with patches

See merge request ghc/head.hackage!5