The nodeset must be freed before the document. Fixes #443.
* In conda or Gentoo Prefix, we don't want to use the system python and instead rely on PATH lookup.
* python/types.c: fix a memory errro when using namespace nodes returned from XPath queries, should fix #521699 * python/tests/Makefile.am python/tests/xpathns.py: add a specific regression test for it Daniel svn path=/trunk/; revision=3703