Patches for GHC MR !8686

These patches adapt to the changes in template-haskell-2.21.0.0
introduced by GHC MR !8686: GADT constructors now take a non-empty list.

Packages affected:

  - freer-simple,  1.2.1.2
  - th-abstraction, 0.4.5.0 and 0.5.0.0
  - true-name, 0.1.0.3