This adds the module `Data.Void` (formerly provided by Edward Kmett's `void`
package) to `base`.

The original Haskell98 compatible implementation has been modified to use
modern GHC features (among others this makes use of `EmptyCase` as
motivated by #2431), and `vacuousM` was dropped since it's redundant now
with the AMP in place.  Instances for classes not part of `base` had to be
dropped as well.

TODO: Documentation could be improved

Reviewed By: ekmett, austin

Differential Revision: https://phabricator.haskell.org/D506