more accessor classes for the parser context, allow to switch on and check

* python/TODO python/generator.py python/libxml2-python-api.xml
  python/libxml2class.txt: more accessor classes for the parser
  context, allow to switch on and check validity
* python/tests/Makefile.am python/tests/error.py
  python/tests/invalid.xml python/tests/valid.xml
  python/tests/validate.py: attded more test and and added error.py
  which I forgot to commit in the last step
Daniel
diff --git a/python/libxml2class.txt b/python/libxml2class.txt
index d952c2c..374fe48 100644
--- a/python/libxml2class.txt
+++ b/python/libxml2class.txt
@@ -333,6 +333,13 @@
 Class parserCtxt()
     # accessors
     doc()
+    isValid()
+    lineNumbers()
+    loadSubset()
+    pedantic()
+    replaceEntities()
+    validate()
+    wellFormed()
 
     # functions from module parser
     clearParserCtxt()