bump libc's version up to 0.2.16 that includes https://github.com/rust-lang/libc/pull/70 and https://github.com/rust-lang/libc/pull/378
bump libc's version up to 0.2.16 that includes https://github.com/rust-lang/libc/pull/70 and https://github.com/rust-lang/libc/pull/378

alexcrichton/net2-rs