The Docbook parser module has been removed completely. Support for
XPointer locations (ranges and points) is disabled by default, and will
eventually be removed completely. Given that the maintainer comments
on the latter: "Be warned that this part of the code base is buggy and
had many security issues in the past", it seems to be prudent to no
longer build with XPointer locations support right away.
To be able to build against libxml2 2.10.0, we remove the export
definitions for Windows.
Closes GH-9358.
