Display source code correctly for decorated functions.

If a function is decorated with a decorator which itself has been
decorated using @decorator, currently the no source code is
displayed when '??' is used. This checks to see if the function
has a __wrapped__ attribate (added by @decorator) and appropriately
displays the source for that object.

IPython/core/oinspect.py

@@ -133,6 +133,9 b' def getsource(obj,is_binary=False):'
     if is_binary:
         return None
     else:
+        #get source if obj was decoratred with @decorator
+        if hasattr(obj,"__wrapped__"):
+            obj = obj.__wrapped__
         try:
             src = inspect.getsource(obj)
         except TypeError: