The function lxc_caps_last_cap() determines CAP_LAST_CAP of the current kernel
dynamically. It first tries to read /proc/sys/kernel/cap_last_cap. If that
fails, because the kernel does not support this interface yet, it loops
through all capabilities and tries to determine whether the current capability
is part of the bounding set. The first capability for which prctl() fails is
considered to be CAP_LAST_CAP.
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>