Make crate libc import public.

[fiveop]

On currently nightly I got an error regarding the public export of libc in sys::ioctl. It now requires us to import the extern crate publicly.

[kamalmarhubi]

I don't fully understand the implications of this. Seems related to #226?

[posborne]

II'm OK with this change and I don't see another way to solve the problem while keeping the ioctl stuff the way it is now (using macros).

[fiveop]

The other option is not exporting libc from ioctl and apparently that breaks things.

[posborne]

Yet another option would be to change the nix::sys::ioctl to use functions that are part of the nix API rather than generating code that directly uses libc. I am somewhat partial to this solution and maybe eliminating the macros completely.

Then again, I'm not sure how many users are depending on the macros. I think they were an interesting experiment but I'm not sure they really make sense in nix and certainly seem to clash with the other exposed APIs to some degree.

[fiveop]

For now, I'd like to get the build working again.

For the discussion on whether to export libc or not we already have #226.

[posborne]

Fair enough, @homu r+

[homu]

📌 Commit 37a2884 has been approved by posborne

[homu]

⌛ Testing commit 37a2884 with merge e0f5444...

[homu]

☀️ Test successful - status