This removes all but the following headers from our includes:
 - attach_options.h
 - lxccontainer.h
 - version.h

This also removes the duplicate lxc_version function (lxc_get_version
has been preferred for a while).

lxclock.h is now considered private.

As a result quite a lot of files needed addition of extra includes
previously inherited from lxclock.h.
Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>