First cut a new mock launcher

[Mike McLean]

Clark Williams wrote:
> Note that the program makes use of Linux namespaces. This *should*
> make our handling of mount points within the chroot (/proc, /sys,
> etc.) a bit easier to clean up, since when the process dies the mounts
> should just go away. I haven't verified this though, so caveat emptor.

Using namespaces does not relieve us of managing our mounts. For 
example, mock.py still needs to make sure the mounts are gone before 
attempting to remove a buildroot. It mainly serves as a safety net.

> #ifdef USE_SELINUX
> 	// add LD_PRELOAD for our selinux lib if selinux is in use is set

I don't think the SELINUX preload needs to be done here anymore. 
mock.py can set it up when running mock-yum if need be.