Improve linkification of man pages in HTML.

If we backtick things, they don't get turned into links; if we don't,
they do!  As a bonus, this doesn't change how the actual man pages look.
Merge improve-man-page-linkification (#49) into master

Improve linkification of man pages in HTML.

If we backtick things, they don't get turned into links; if we don't,
they do!  As a bonus, this doesn't change how the actual man pages look.