Regenerate the checked-in HTML for the man pages.

The HTML files were generated automatically using

  sudo apt-get install troffcvt
  make man-html

But I have also changed the man source files to ensure that
the generated output still looks nice.  The changes were
mainly replacing blank lines with ".PP", but there were a
few other tweaks needed too.

Tested by viewing the output on both Chrome and Safari,
and using "man" and (equivalently) "nroff -man" and
examining the changes.

Reviewed by Craig Silverstein.