Publish a new version of libc to unquote std crate

[SSheldon]

Now that rust-lang/rust#23786 is merged, publishing a new version of libc should fix the note: use an identifier not in quotes instead warning.

[sfackler]

@alexcrichton Ping, liblibc's broken on the new nightly

[alexcrichton]

The repo as-is won't work due to rust-lang/rust#23811 but I have pushed a new version which works.