applied patch from Stéphane Bidoul to fix some Python bindings

* python/libxml.c python/generator.py python/libxml.py
  python/libxml2-python-api.xml python/libxml2class.txt:
  applied patch from Stéphane Bidoul to fix some Python bindings
  initialization, then had to change the parserCleanup()
  to handle memory released there.
* xmlmemory.c: added more debugging comments.
Daniel
diff --git a/python/libxml2-python-api.xml b/python/libxml2-python-api.xml
index d5a4cbe..f6ecd83 100644
--- a/python/libxml2-python-api.xml
+++ b/python/libxml2-python-api.xml
@@ -306,5 +306,9 @@
       <return type='int' info="The error line" field="line"/>
       <arg name='Error' type='xmlErrorPtr' info='the Error'/>
     </function>
+    <function name='xmlPythonCleanupParser' file='python'>
+      <info>Cleanup function for the XML library. It tries to reclaim all parsing related global memory allocated for the library processing. It doesn't deallocate any document related memory. Calling this function should not prevent reusing the library but one should call xmlCleanupParser() only when the process has finished using the library or XML document built with it.</info>
+      <return type='void'/>
+    </function>
   </symbols>
 </api>