kernel: allow features to be used in common-config

Signed-off-by: Austin Seipp <aseipp@pobox.com>
kernel: only use DEBUG_STACKOVERFLOW if !grsecurity

Signed-off-by: Austin Seipp <aseipp@pobox.com>
kernel/grsec: another optional option

This should fix the testing kernels.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
kernel/grsec: disable vserver packages for now

Fixing this will require some fiddling due to the odd version number;
see the Hydra build logs for more.

Signed-off-by: Austin Seipp <aseipp@pobox.com>