rules/control-structᵒ: (if (not test) a b) => (if-not test a b)

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
rules/control-structᵒ: New rule to transform single-branch if/if-not

Signed-off-by: Gergely Nagy <algernon@balabit.hu>