[RFC] Initial integration of libct into libcontainer

Hi Victor and Michael,

I'm starting to integrate libct with libcontainer. I would like to share
with you this early draft to gather your opinions and advices.

This patch adds new factory and container classes to create and manage
containers via LibCT. This version is based on Michael's
version, where is a new api is used. It has minimal functionality just
to show you how it looks like.

Here are a few questions:

* Are you going to implement a new api in libcontainer?
* May we have two implementations, while libct doesn't cover all
functionality of libcontainer?

Notes:

The dockerinit process isn't required for libct. If I understand
correctly, dockerinit is used, because in golang code we should make
os.exec() immediately after os.clone().

dockerinit must be built w/o libct, because it's executed from
containers, where the libct library and its dependencies are absent.

Note: compiled with docker 0c5d9626b82e97ef34b3c13bb581f0aadc0bffe2

Cc: Michael Crosby <michael@docker.com>
Cc: Victor Marmol <vmarmol@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
SetParentDeathSignal
libct: set bset