Problem is, <meta ...></meta> is in HTML as illegal as <meta .../>.  For
those singleton tags, there is IMO no way of generating code which
validates for HTML /and/ XHTML.

My proposal:
- a Python script roundup-fixtemplates.py which reads the config setting
  and changes (if told to) the templates accordingly
- the script would change the templates in-place and create backups
  (.html~, .html~2) if desired
- would the script need to read/write the checksum line?
  (What purpose does this fulfill anyway?)