plugins: std -- Implement std_memcpy

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
plugins: std -- Add fcntl constants

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
plugins: fds -- Add file descriptor transmission helpers

This plugin implements send_fds/recv_fds functions. Thus
if some plugin needs file transfer over unix socket it
might use them.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>