Linebreaks between definitions don't respect `#:indent`

[jackfirth]

The expression (program-format "(define x 1) (define y (* x 2))" #:indent 2) produces this code:

(define x 1)
(define y (* x 2))

But to be correct with respect to the #:indent 2 argument, it should produce this:

(define x 1)
  (define y (* x 2))

This issue seems related to #68. This isn't intended behavior, is it?