applied and fixed a patch from Stephane Bibould to provide per parser

* python/generator.py python/libxml.c python/libxml.py
  python/libxml_wrap.h python/types.c: applied and fixed a patch
  from Stephane Bibould to provide per parser error handlers at the
  Python level.
* python/tests/Makefile.am python/tests/ctxterror.py: added a
  regression test for it.
Daniel
diff --git a/python/generator.py b/python/generator.py
index 9adbfbe..f8a1e0b 100755
--- a/python/generator.py
+++ b/python/generator.py
@@ -290,6 +290,8 @@
 def skip_function(name):
     if name[0:12] == "xmlXPathWrap":
         return 1
+    if name == "xmlFreeParserCtxt":
+        return 1
 #    if name[0:11] == "xmlXPathNew":
 #        return 1
     return 0
@@ -618,6 +620,7 @@
     "xmlAttribute" : "xmlNode",
     "outputBuffer": "ioWriteWrapper",
     "inputBuffer": "ioReadWrapper",
+    "parserCtxt": "parserCtxtCore",
 }
 classes_destructors = {
     "parserCtxt": "xmlFreeParserCtxt",