Fixes linking on windows

[nkpart]

Using 7.10.1 and 7.10.2 on windows, the GHC rts memory barrier functions are unavailable. The code was trying to avoiding using these functions but on my systems I had 2 problems:

• the _WIN32 and _WIN64 defines weren't present
• the cabal file was not building in RtsDup.c (once the defines were changed)

For the defines, I used this page (https://downloads.haskell.org/~ghc/7.10.2/docs/html/users_guide/options-phases.html#c-pre-processor) and the command stack exec ghc -- -E -optP-dM -cpp test.hs to check what was available.

And yeah, the cabal file just wasn't building the RtsDup file.

[rrnewton]

Thanks! We've had windows testing on our Jenkins setup at times. But we weren't very good at keeping it up, so this is much appreciated.

[ethercrow]

Could you make a hackage release with this commit please?

[nkpart]

+1, @rrnewton. That would be clean up the only non-hackage dependency in my project :)

[rrnewton]

Sorry, guys. We need a backup maintainer because I'm slow.. @DreamLinuxer would you be able to be a second maintainer on hackage for atomic-primops and related packages?

This is uploaded now as atomic-primops-0.8.0.2.

Thanks again for the PR!

[DreamLinuxer]

OK, I can be the second maintainer.