Document API: fix DAV handlers that contain "-"

Many DAV properties are like "calendar-data", which has to be translated
to _prefix_"calendar_data" for a pythonic function.

bzr revid: p_christ@hol.gr-20100729133938-hqshcsqtdrm6n2yc

addons/document/nodes.py

@@ -301,7 +301,7 @@ class node_class(object):
             logger.debug('No namespace: %s ("%s")',ns, prop)
             return None
 
-        mname = prefix + "_" + prop
+        mname = prefix + "_" + prop.replace('-','_')
 
         if not hasattr(self, mname):
             return None