Win32 Backports to release branches

Hi,

I need to backport a small fix in Win32 to all active release branches. https://github.com/haskell/win32/commit/530c5ec7d98edf77f2605afed8449f62f45ae93b

I can create new tags for a minor revision for the versions bundled by GHC, but I need to know which versions are open for backports (I haven't followed the policy changes).

/cc @bgamari

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