Fix Python bindings under Windows

- Correct linker flags for MinGW-w64
- Adjust PATH to find libxml2.dll when running tests

python/tests/Makefile.am

@@ -66,6 +66,7 @@ tests: $(PYTESTS)
 	   export PYTHONPATH; \
 	   LD_LIBRARY_PATH="$(top_builddir)/.libs:$$LD_LIBRARY_PATH" ; \
 	   export LD_LIBRARY_PATH; \
+	   export PATH="$(top_builddir)/.libs:$$PATH" ; \
 	   for test in $(PYTESTS) ; \
 	   do log=`$(PYTHON) $(srcdir)/$$test` ; \
 	   if [ "`echo $$log | grep OK`" = "" ] ; then \