* add UL_ENABLE_ALIAS(NAME, MASTERNAME) to initialize $enable_<name>
according to MASTERNAME. Note that we have to use $build_<mastername>,
the $enable_<mastername> is just AC_ARG_ENABLE() stuff only. The
$build_ is evaluated and modified by our UL_...() functions.
* add enable-schedutils.conf to have build-system regression test for
this use-case
Addresses: https://github.com/karelzak/util-linux/issues/415
Signed-off-by: Karel Zak <kzak@redhat.com>