rules/optimᵒ: Support defun, defn-alias and defun-alias too

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
rules/syntaxᵒ: New ruleset

Moved the (defn a (x)) => (defn a [x]) ruleset here, as that is not an
optimisation.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Simplify two condᵉs

When unifying a single LVar within a condᵉ to N different things, we can
do that with a memberᵒ instead, which is much clearer, shorter and more
extensible.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>