* python/generator.py: added a check on the argument for some
  classes (e.g. xmlDoc and xmlNode) to prevent a segfault (as
  reported on the list).  Further enhancement should be done
  to auto-create the appropriate object.
* python/libxml.c: minor fix for a warning message; added a
  routine, currently not used, to report the description of a
  PyCObject.
* python/libxml2class.txt: regenerated