Inline monoid instance for Unit can't possibly do anything useful.
Inline monoid instance for Unit can't possibly do anything useful.

`a` was a strict unit, left `b` as it is lazy, but I would
_hope_ it could be removed with no effect.

Note this change was driven by warning generated by scala 2.10.0
for discarding result of `a`. Possibly a silly warning, but I
think the change holds.

xuwei-k/scala-machines,runarorama/scala-machines