With this, `pdf` can print info for CIPA_DC-003-2020_E.pdf
(from https://cipa.jp/e/std/std-sec.html), as well as all other
files I've tried.
CIPA_DC-003-2020_E.pdf is special because it quits this loop after
exactly 64 interations, at round_number 63.
While here, also update a comment to use the non-spec-comment style
I'm now using elsewhere in the file.
f956cd6e6a