configure.ac: Make our configure more consistent

This commit does the following changes:
 - Disable rpath by default
 - Switch all of our options to --enable-FEATURE in the help
 - Add auto-detection of libcap availability
 - Add auto-detection of python3 availability
 - Always specify the default value in --help
 - Add a configuration overview at the end

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
make mountcgroups hook to lxc.include aware (v2)

[resending the patch from correct branch]

commit 09ad624693cb0ef41cf246e2876b5f356783b34d introduced lxc.include option
to include other config files. This patch uses it in mountcgroups hook otherwise
lxc-start fails with following error message for the nested containers;

root@oOo:/var/lib/lxc/raring# lxc-start -l debug -o l -n raring -d
lxc-start: command get_cgroup failed to receive response

Signed-off-by: S.Çağlar Onur <caglar@10ur.org>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
stop: add nolock option

If the system gets into a bad state, it may become impossible to get
the lxc container locks.  We should still be able to stop containers
in that case.  Add a -L/--nolock option to specify this behavior.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
lxc_conf_free: free rootfs.pivot and log_file if not null

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>