[xml] libxml2 2.7.1 breaks XML serialisation of HTML trees

["Stefan Behnel" <stefan_ml behnel de>]

Hi,

there was a change in 2.7.1 (xmlsave.c, ~760) that prevents HTML documents
from being serialised in XML style. That was actually a very convenient
feature in lxml, where you could select between XML and HTML serialisation
of an HTML tree based on a keyword argument.

I now wonder why there are two serialisation methods (xmlNodeDump* and
htmlNodeDump*) that ultimately do the same thing, instead of serialising
to what they are named after.

If the current behaviour is wanted, what's the future way of achieving
this *without* temporarily modifying the document? (i.e. without breaking
thread concurrency)

Stefan