Add journald logging datatypes on non-Linux

[matthewbauer]

These need to be available in some cases.

[3noch]

Can we just use #7 instead?

[3noch]

IIRC depending on journald in cabal prevents mac support so using a cabal flag as #7 does allows you to choose this at the dependency level.

[Ericson2314]

As I commented on 345a0e2, I think that turning of a compiler error into a runtime error was a bad idea, and that was the domino that necessitates this. @3noch's proposal to be static and explicit (say what you mean in the CPP) is I think the right approach, and in the opposite direction.

[matthewbauer]

I don't see how introducing a cabal flag improves the situation besides making things more confusing. The issue was introduced in 345a0e2. I guess it's debatable whether it should be a runtime error or a type error though... But if it's a runtime error, this is needed to get things working again.

[ali-abrar]

Are users ever expected to write code that uses this constructor? If so, I'd rather not force CPP into user code, but if not we can revert 345a0e2 and replace with another approach.

[ali-abrar]

What happened to this commit, I wonder: 9146836 @luigy

[3noch]

Haha we've implemented the same thing multiple times!

[ali-abrar]

Closing in favor of #38