Decide what to do about repeating patterns with an odd number of rows

[bamarsha]

For complicated reasons, these two patterns aren't equivalent:

pattern a
  garter.
  garter.
end

pattern b
  repeat 2
    garter.
  end
end

I think the current behavior kind of makes sense but it's definitely confusing, so we should document it somewhere. Or consider changing the behavior to something more intuitive but I'm not sure if there's a way to do it that makes sense in every case... @logicologist