[Htmlvalidator-help] multi threaded line numbering - improved

[[LoN]Kamikaze <LoN...@gm...>]

I recognized that my algorithm does not recognize nested line breaks. So
here is a version that reorganizes the document until all line breaks
are direct children of the <pre> tags.

I also fixed the line numbering calls to use setTimeout(), to spawn the
line numbering in a different thread, so that Firefox keeps reacting
while everything is prepared to start the parallel threaded part of the
line numbering.

Also I removed a bug where lines disappeared when a <pre> only contains
a single line, which is the case in about:blank.

On my Pentium-M 1300 MHz your lot_of_lines.html takes 32 seconds. That
means it does 341 lines per second, which is OK for me, considering the
massive amount of parsing and restructuring that is done.