more precise dashes in man pages

Groff 1.23 changes the way bare dashes are interpreted:¹

  The hyphenation patterns for English have been updated using the
  `hyph-en-us.tex` patterns file from the TeX hyph-utf8 project.  The
  new patterns likely _will_ change the automatic hyphenation break
  points of your English documents.
  …
  The an (man) and doc (mdoc) macro packages no longer remap the -, ',
  and ` input characters to Basic Latin code points on UTF-8 devices,
  but treat them as groff normally does (and AT&T troff before it did)
  for typesetting devices, where they become the hyphen, apostrophe or
  right single quotation mark, and left single quotation mark,
  respectively.  This change is expected to expose glyph usage errors in
  man pages.  See the "PROBLEMS" file for a recipe that will conceal
  these errors.  A better long-term approach is for man pages to adopt
  correct input practices; the man pages groff_man_style(7),
  groff_char(7), and man-pages(7) (subsection "Generating optimal
  glyphs"; from the Linux man-pages project) contain such instructions.
  Doing so also improves man page typography when formatting for PDF.

This is already causing controversy and Debian has patched it back to the old
behavior.² LWN has a good summary of why such a seemingly minor display change
has acute negative consequences.³

¹ https://lists.gnu.org/archive/html/info-gnu/2023-07/msg00001.html
² https://lwn.net/ml/debian-devel/ZS0aV4XyJH+O1o%2Fc@riva.ucam.org/
³ https://lwn.net/Articles/947941/