Use libc for FFI functions and constants

Author: Susurrus

CHANGELOG.md

@@ -23,6 +23,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#647](https://github.com/nix-rust/nix/pull/647))
 - Exposed `unistd::setresuid` and `unistd::setresgid` on FreeBSD and OpenBSD
   ([#721](https://github.com/nix-rust/nix/pull/721))
+- The `addr` argument to `madvise` is now `*mut` to better match the
+  libc API.
 
 # Fixed
 - Fix compilation and tests for OpenBSD targets

Cargo.toml

@@ -15,7 +15,7 @@ exclude     = [
 ]
 
 [dependencies]
-libc = { git = "https://github.com/rust-lang/libc" }
+libc = { git = "https://github.com/susurrus/libc", branch = "mman_constants" }
 bitflags = "0.9"
 cfg-if = "0.1.0"
 void = "1.0.2"