Attempt at generating useful html files.
To try:
 - set log_html = true in debug.ml
 - copy or move generated stdout to stdout.html
Notes:
 - it uses semantic tags, so if log_html is false then output is as before
 - one caveat to the above statement is that this might have broken terminal colours
 - tag closing does not seem to be completely predictable, I had some troubles getting details tags closed.