Auto merge of #1951 - KentaTada:add-sockoptions-consts, r=JohnTitor
Auto merge of #1951 - KentaTada:add-sockoptions-consts, r=JohnTitor

Add constants of socket options

Signed-off-by: Kenta Tada <bfcbc6141feda87cbc58e846dfb8f4969098b30b@sony.com>

rust-lang/libc,rust-lang/libc,rust-lang/libc