xmlTextReader bails too quickly on error

For https://bugzilla.gnome.org/show_bug.cgi?id=654567
I use xmlTextReader to parse failed that might be incomplete.  These files are
the beginning of a well-formed file, but the end is missing so the file as a
whole is not well-formed.

The problem is that xmlTextReader starts returning errors when it encounters
the early EOF, even though I haven't finished reading all of the valid data in
the file.  It would be helpful if xmlTextReader kept working until the very
end.