Make all libcurl related options use .nf (no fill) for the SYNOPSIS
section - for consistent look. roffit then renders that section using
<pre> (monospace font) in html for the website.
Extended manpage-syntax (test 1173) with a basic check for it.
Closes#8062
- avoid writing "set ..." or "enable/disable ..." or "specify ..."
*All* options for curl_easy_setopt() are about setting or enabling
things and most of the existing options didn't use that way of
description.
- start with lowercase letter, unless abbreviation. For consistency.
- Some additional touch-ups
Closes#7688
