include/debug: make masknames optional

Signed-off-by: Karel Zak <kzak@redhat.com>
include/debug: cleanup masks

Signed-off-by: Karel Zak <kzak@redhat.com>
include/debug: allow to speficy empty masknames

Signed-off-by: Karel Zak <kzak@redhat.com>
tests: add debug tests

Signed-off-by: Karel Zak <kzak@redhat.com>
Signed-off-by: Ondrej Oprala <ooprala@redhat.com>