Unix: add getgrnam_r and getgrgid_r
Unix: add getgrnam_r and getgrgid_r

rust-lang-nursery/libc,rust-lang-nursery/libc,rust-lang-nursery/libc,cactorium/libc,rust-lang/libc,rust-lang/libc,cactorium/libc,rust-lang/libc,cactorium/libc