hardened the addChild function added accessors needed for xmlNode, a bit

* tree.c: hardened the addChild function
* python/generator.py python/libxml.c python/libxml2-python-api.xml
  python/libxml2class.txt python/libxml_wrap.h python/TODO:
  added accessors needed for xmlNode, a bit more testing and
  extension of interfaces
* python/tests/Makefile.am python/tests/build.py: added a test
  build from scratch/save/load/check
Daniel
diff --git a/python/tests/Makefile.am b/python/tests/Makefile.am
index 76bf897..e468e6c 100644
--- a/python/tests/Makefile.am
+++ b/python/tests/Makefile.am
@@ -1,6 +1,7 @@
 EXAMPLE_DIR = $(prefix)/share/doc/libxml2-python-$(LIBXML_VERSION)/examples
 
 TESTS=		\
+    build.py	\
     tst.py	\
     tstxpath.py	\
     xpathext.py	\