* xinclude.c: fixed xmlXIncludeParseFile to prevent
  overwriting XML_COMPLETE_ATTRS when setting pctxt->loadsubset
  (bug 166199)
* Makefile.am, python/tests/Makefile.am, xstc/Makefile.am: added
  code to add $(top_builddir)/.libs to LD_LIBRARY_PATH whenever
  PYTHONPATH is set, to assure new libxml2 routines are used.