Alec Theriault authored
`parallel` is used in exactly one place in the GHC tree: the T2317 test. It seems almost by accident that it is a submodule; libraries needed only for tests should net be included as submodules (see `QuickCheck`, `async`, `haskell98`, `regex-compat`, `utf8-string`, `vector` and more for examples). T2317 will now get run only when `parallel` is installed instead of `parallel` being required for the testsuite to run.
Code owners : Ben Gamari