ctfconvert.1: Minor cleanup

Alphabetize option table to improve first glance access.
Markup semantics to differentiate them and add them to apropos.

MFC after: 3 days
Reviewed by: Pau Amma <pauamma@gundo.com>
Approved by: mhorne (mentor, implicit)
Differential Revision: https://reviews.freebsd.org/D49883