Add #defines for "Expect" header, which is a part of RFC 2616 and used for HTTP PUT/POST operations. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Hegde, Nagaraj P <nagaraj-p.hegde@hpe.com> Reviewed-by: Samer El-Haj-Mahmoud <elhaj@hpe.com> Reviewed-by: Jiaxin Wu <jiaxin.wu@intel.com> Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>