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
Stick to "Schannel" everywhere. The configure option --with-winssl is
kept to allow existing builds to work but --with-schannel is added as an
alias.
Closes#3504
