Auto merge of #491 - Roguelazer:add_getpeereid_function, r=alexcrichton
Auto merge of #491 - Roguelazer:add_getpeereid_function, r=alexcrichton

Add getpeereid function

This is a wrapper around getsockopt() for getting the uid/gid of a remote Unix domain socket peer. It was added in FreeBSD 4.6 and present in all modern BSDs I checked (including Mac OS X).

mneumann/libc,anatol/libc,philippkeller/libc,superriva/libc,rust-lang/libc,mneumann/libc,cactorium/libc,cactorium/libc,philippkeller/libc,rust-lang/libc,rust-lang-nursery/libc,mneumann/libc,superriva/libc,philippkeller/libc,superriva/libc,cactorium/libc,anatol/libc,anatol/libc,rust-lang-nursery/libc,rust-lang/libc,rust-lang-nursery/libc