fix confusing target doc cfg

[conradludgate]

fixes #201

The Debug impl is still incorrect, but this is an improvement nonetheless.

[complexspaces]

This seems like a much better spot to me even if all the cross-platform weirdness isn't gone yet.

IIUC this PR correctly, we are now overriding rustdoc's automatic availability generation and replacing it with manual declarations that new and impl ServerCertVerifier are available everywhere and that new_with_extra_roots is available everywhere but Android all without caring about the underlying OS the docs are built on.

[djc]

Thanks!

[ofek]

Thanks! Out of curiosity, what is the long-term fix/standard practice for such situations? I assume it's somehow about moving to a single interface with methods that are implemented by calling internal functions that are conditional at build time but I'm not certain.

[Ralith]

Static indirection through a facade seems like the way to go, yeah.