* guix/read-print.scm (<vertical-space>, vertical-space?)
(vertical-space, vertical-space-height): New variables.
(combine-vertical-space, canonicalize-vertical-space)
(read-vertical-space): New procedures.
(read-with-comments): Use it in the #\newline case.
(pretty-print-with-comments): Add #:format-vertical-space and honor it.
Add case for 'vertical-space?'.
* guix/scripts/style.scm (format-package-definition): Pass
#:format-vertical-space to 'object->string*'.
* tests/read-print.scm ("read-with-comments: list with blank line")
("read-with-comments: list with multiple blank lines")
("read-with-comments: top-level blank lines")
("pretty-print-with-comments, canonicalize-vertical-space"): New tests.
Add a couple of additional round-trip tests.
* guix/read-print.scm (<blank>, blank?): New record type.
(<comment>): Redefine using the record interface.
(read-with-comments, pretty-print-with-comments): Change some uses of
'comment?' to 'blank?'.
* guix/scripts/style.scm (simplify-inputs)[simplify-expressions]: Use
'blank?' instead of 'comment?'.
* guix/read-print.scm (<comment>): Rename constructor to
'string->comment'.
(comment): New procedure.
(read-with-comments, canonicalize-comment): Use 'string->comment'
instead of 'comment'.
