Library proposal: Add System.Info.isWindows

[Neil Mitchell]

Hi

> There are many examples in Cabal, almost all of them just distinguish
> windows vs non-windows

Perhaps this suggests that we should leave the full OS choice for a
while, until we can pick "the right thing", and do exactly what my
original proposal suggested - test for one single thing that is a very
common pattern which people often get wrong.

If the only reason for not just adding isWindows is "politics" then I
think its clearly the only sensible choice :-)

Thanks

Neil