fixed doc comment problems adding RelaxNG wrappers added a specific test

* xpath.c: fixed doc comment problems
* python/generator.py python/libxml_wrap.h python/types.c: adding
  RelaxNG wrappers
* python/tests/Makefile.am python/tests/relaxng.py: added a specific
  test of those early Python RelaxNG bindings
Daniel
diff --git a/xpath.c b/xpath.c
index 4bbb7dd..69a3910 100644
--- a/xpath.c
+++ b/xpath.c
@@ -8176,7 +8176,7 @@
 }
 
 /**
- * xmlXPathCompExpr:
+ * xmlXPathCompileExpr:
  * @ctxt:  the XPath Parser context
  *
  *  [14]   Expr ::=   OrExpr 
@@ -10610,7 +10610,7 @@
  *
  * Compile an XPath expression
  *
- * Returns the xmlXPathObjectPtr resulting from the evaluation or NULL.
+ * Returns the xmlXPathCompExprPtr resulting from the compilation or NULL.
  *         the caller has to free the object.
  */
 xmlXPathCompExprPtr