make @interactive decorator friendlier with dill

sets the decorated function globals to main,
in addition to just the module name.

This helps dill treat it as if it were defined locally,
and the function actually behaves the same locally as it does on engines.

IPython/parallel/util.py

@@ -27,6 +27,7 b' try:'
     from signal import SIGKILL
 except ImportError:
     SIGKILL=None
+from types import FunctionType
 
 try:
     import cPickle
@@ -221,8 +222,16 b' def interactive(f):'
     This results in the function being linked to the user_ns as globals()
     instead of the module globals().
     """
-    f.__module__ = '__main__'
-    return f
+    mainmod = __import__('__main__')
+    
+    # build new FunctionType, so it can have the right globals
+    # interactive functions never have closures, that's kind of the point
+    f2 = FunctionType(f.__code__, mainmod.__dict__,
+        f.__name__, f.__defaults__,
+    )
+    # associate with __main__ for uncanning
+    f2.__module__ = '__main__'
+    return f2
 
 @interactive
 def _push(**ns):