More on the libxml2 update situation

So I did a routine software update on my RHEL6 workstation, and noticed
a security update for libxml2 go by.  And guess what: now an XML-enabled
build of Postgres fails regression tests for me, just as previously
discussed in
http://www.postgresql.org/message-id/flat/CAFj8pRA4xJQFGNQCqMCYGx-umgMr3Stt3xFEUw7kBsOiOvGhkA@mail.gmail.com

A little bit of digging shows that the behavior we're unhappy about was
introduced as part of the official patch for CVE-2015-7499.  This means
that, whether or not we can persuade Veillard that it was a bad idea and
he should undo it, the bogus behavior is likely to spread into mainstream
distributions a lot faster than any followup fix will :-(.  Bugfix updates
just don't get accepted as quickly as security updates.

I'm starting to think that maybe we'd better knuckle under and provide
a variant expected file that matches this behavior.  We're likely to be
seeing it in the wild for some time to come.
        regards, tom lane