Don't conditionally define datatypes etc

[igfoo]

The network package conditionally defines things depending on the capabilities of the platform, e.g.:

data Family
    =
[...]
#ifdef AF_INET6
    | AF_INET6            -- Internet Protocol version 6
#endif
[...]

This makes it impossible to write portable programs. Please instead define the datatypes etc unconditionally, and change the code so that, for example, it throws an exception if an unsupported family is used, and perhaps also provide functions like

supportedFamily :: Family -> Bool

[tibbe]

I'm in favor of this.

[bmillwood]

Despite the above pull request, I think there's more to be done. There are still a few functions, especially IPv6 stuff, that are only conditionally exported.

[tibbe]

@BenMachine Agreed. We just need to sort out exactly what to do.

[kazu-yamamoto]

Already implemneted.