libct: add initial go bindings

This patch is a prototype. I'm going to implement all other functions,
when all of you will say that it's what we want.

Cc: Michael Crosby <crosbymichael@gmail.com>
Cc: Dmitry Guryanov <dguryanov@parallels.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
mount: add flags NOEXEC, NOSUID, NODEV, STRICTATIME

All these flags are used by libcontainer.
ct: return pid from spawn_execve()
ct: allow to set pdeathsig
libct: build a static version of the library

It will be used for libcontainer. libcontainer is used by tools,
which are executed in a container and libct may be not installed there.

Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Merge pull request #15 from avagin/xemul

Here are patches which are required for integration with libcontainer