Bump haddock[-api] to 2.24.2

Bump haddock[-api] to 2.24.2

Merge pull request haskell#1354 from Kleidukos/ci/select-cabal-3.4.0.0

Select Cabal 3.4.0.0 instead of 3.4 in CI

Merge pull request haskell#1354 from Kleidukos/ci/select-cabal-3.4.0.0

Select Cabal 3.4.0.0 instead of 3.4 in CI

Merge pull request haskell#1354 from Kleidukos/ci/select-cabal-3.4.0.0

Select Cabal 3.4.0.0 instead of 3.4 in CI

Update README

Removed some out of date links/info, added some more useful links.

  * badge to Hackage
  * update old trac link
  * `ghc-head` => `ghc-8.10`
  * `cabal new-*` is now `cabal v2-*` and it should Just Work
  * `--test-option='--accept'` is the way to accept testsuite output

Prepare an unexpected 2.23.1 release

Unfortunately, the 2.23.0 release is broken on 8.8.2 and 8.8.3. However,
there is no good backwards compatible fix. The fix going forward is:

  - Revise already release `haddock-api-2.23.0` to build only on
    `ghc-8.8.1` (this is the truth - it won't build on 8.8.2 or 8.8.3)

  - Release `haddock-api-2.23.1` and `haddock-2.23.1` to build only on
    `ghc-8.8.2` and `ghc-8.8.3`

Given that there are hardly any commits between these two releases, and
this is mostly one (not user visible) backwards incompatible change,
the changelog won't be updated.

Fix Travis CI, loosen .cabal bounds (haskell#1089)

Tentatively for the 2.23 release:

  * updated Travis CI to work again
  * tweaked bounds in the `.cabal` files
  * adjusted `extra-source-files` to properly identify test files

Release `haddock{,-api}-2.22.0`

This version will accompany ghc-8.6.2

Bump haddock-library to 1.7.0

The 1.6.1 release should've been a major bump, since types in
the `Documentation.Haddock.Parser.Monad` module changed. This version
makes that module internal (as it morally should be).