fdformat: Some minor change to the manual

fdformat: Some minor change to the manual

  \- changed to - (code "hyphen-minus", rendered with the glyph hyphen
in troff) if it is a part of a compound name.  A minus is not used in
words.  People using UTF-8 and copy-and-pase can(?) (may?) use "info",
"man --ascii" or the command "man" should have an option to display the
- in names of options with the code (character name) "hyphen-minus"
(u002D) instead of "u2010" (code (character) name "hyphen")

Signed-off-by: Karel Zak <kzak@redhat.com>