Do not import deprecated functions from external decorators library.

Closes gh-470

IPython/external/decorator/__init__.py

@@ -1,8 +1,4 b''
 try:
     from decorator import *
-    from decorator import getinfo, new_wrapper
-    # the following funcion is deprecated so using the python own one
-    from functools import update_wrapper
 except ImportError:
     from _decorator import *
-    from _decorator import getinfo, update_wrapper, new_wrapper

IPython/testing/decorators.py

@@ -56,7 +56,7 b' import unittest'
 # Third-party imports
 
 # This is Michele Simionato's decorator module, kept verbatim.
-from IPython.external.decorator import decorator, update_wrapper
+from IPython.external.decorator import decorator
 
 # We already have python3-compliant code for parametric tests
 if sys.version[0]=='2':