Introduce apparmor support

Introduce apparmor support

This could be done as generic 'lsm_init()' and 'lsm_load()' functions,
however that would make it impossible to compile one package supporting
more than one lsm.  If we explicitly add the selinux, smack, and aa
hooks in the source, then one package can be built to support multiple
kernels.

The smack support should be pretty trivial, and probably very close
to the apparmor support.

The selinux support may require more, including labeling the passed-in
fds (consoles etc) and filesystems.

If someone on the list has the inclination and experience to add selinux
support, please let me know.  Otherwise, I'll do Smack and SELinux.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>