[xml/sgml-pkgs] Bug#746811: Bug #746811: Should build against and link with system's libtrio

[Aron Xu]

Control: tags 746811 + wontfix

Yes but this cannot be done, src:libtrio is not in testing, nor any
previous stable releases, also the code are changed quite a lot. If we
really make libxml2 depend on it then I'm afraid we are risking to not
have any new version of libxml2 migrate into testing.

Thanks,
Aron