rules/syntaxᵒ: Add -> related rules

The first two rules were contributed by Nicolas Dandrimont
<nicolas.dandrimont@crans.org>, the others build upon that foundation.

These combined can either transform a long chain of calls into a ->
threading macro, or destructure a short -> into function calls instead.

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