Patch: Regenerating HTML man pages 🔗 link

Hi,

while building the Debian package of xymon I noticed two issues with
re-generating the HTML man pages:

a) Generating the man pages places the current day in the header, so
   the files cannot be generated reproducible (see
   https://en.wikipedia.org/wiki/Reproducible_builds).  Using
   SOURCE_DATE_EPOCH (if it is set) solves this problem.

b) Without "-H localhost" as parameter of man2html the generated HTML
   files differ from what is packaged in the tarball.  So I added this
   option.

The attached patch implements these two cases.

Greetings
Roland