try to fix a problem with valgrind. applied memory leak fix from Brent

* Makefile.am doc/examples/Makefile.am python/tests/Makefile.am
  xstc/Makefile.am: try to fix a problem with valgrind.
* python/generator.py python/libxml.c python/tests/Makefile.am
  python/tests/tstmem.py: applied memory leak fix from Brent Hendricks
  c.f. bug #165349
Daniel
diff --git a/python/generator.py b/python/generator.py
index f2c7939..8add0a9 100755
--- a/python/generator.py
+++ b/python/generator.py
@@ -344,6 +344,8 @@
     # the next function is defined in libxml.c
     if name == "xmlRelaxNGFreeValidCtxt":
         return 1
+    if name == "xmlFreeValidCtxt":
+        return 1
 #
 # Those are skipped because the Const version is used of the bindings
 # instead.