Move Void to GHC.Base...
Move Void to GHC.Base...
This change would allow Void to be used deeper in module graph.
For example exported from Prelude (though that might be already
possible).
Also this change includes a change stimes @Void _ x = x,
See https://github.com/haskell/core-libraries-committee/issues/95
While the above is not required, maintaining old stimes behavior
would be tricky as GHC.Base doesn't know about Num or Integral,
which would require more hs-boot files.