Use libc's syscall declaration.

[fiveop]

Another proposal for fixing an issue ( #341 ). I decided against removing the module, since the constants defined in there are used and they are not defined in libc.

[kamalmarhubi]

@fiveop

since the constants defined in there are used and they are not defined in libc.

Do you mean the constants are used inside nix, or by users of nix? I think if within nix, we should get rid of any such uses. For users of nix, I think the eventual destiny of this module is to be removed, so it's a matter of when they have to work around that. Or do you think the module should remain, even if all constants are added to libc?

[kamalmarhubi]

A heroic PR on libc is in progress to bring in the syscall numbers: rust-lang/libc#374

[kamalmarhubi]

At least on Linux

[fiveop]

I was about to close this PR, when you started your triaging spree. I think #341 is enough of a reminder, and once I or someone else feels like it, can start afresh. So let's close it.