Log Message:
catch up with libxml2 update and update to 2.6.11

Python related changes:

2.6.11: July 5 2004:
   - bug fixes: C14N bug serializing namespaces (Aleksey Sanin), testSAX
    properly initialize the library (William), empty node set in XPath
    (William), xmlSchemas errors (William), invalid charref problem pointed
    by Morus Walter, XInclude xml:base generation (William), Relax-NG bug
    with div processing (William), XPointer and xml:base problem(William),
    Reader and entities, xmllint return code for schemas (William), reader
    streaming problem (Steve Ball), DTD serialization problem (William),
    libxml.m4 fixes (Mike Hommey), do not provide destructors as methods on
    Python classes, xmlReader buffer bug, Python bindings memory interfaces
    improvement (with Stéphane Bidoul), Fixed the push parser to be back to
    synchronous behaviour.
   - improvement: custom per-thread I/O enhancement (Rob Richards), register
    namespace in debug shell (Stefano Debenedetti), Python based regression
    test for non-Unix users (William), dynamically increase the number of
    XPath extension functions in Python and fix a memory leak (Marc-Antoine
    Parent and William)

2.6.10: May 17 2004:
   - portability: problem with xpath.c on Windows (MSC and Borland), memcmp
    vs. strncmp on Solaris, XPath tests on Windows (Mark Vakoc), C++ do not
    use "list" as parameter name, make tests work with Python 1.5 (Ed
  Davis),