Remove some now-obsolete generator future statements.

I left the email pkg alone; I'm not sure how Barry would like to handle
that.

Lib/difflib.py

 #! /usr/bin/env python
 
-from __future__ import generators
-
 """
 Module difflib -- helpers for computing deltas between objects.
 

Lib/test/test_generators.py

-from __future__ import generators
-
 tutorial_tests = """
 Let's try a simple generator:
 

Lib/test/test_parser.py

@@ -27,14 +27,10 @@ class RoundtripLegalSyntaxTestCase(unittest.TestCase):
         self.roundtrip(parser.suite, s)
 
     def test_yield_statement(self):
-        self.check_suite("from __future__ import generators\n"
-                         "def f(): yield 1")
-        self.check_suite("from __future__ import generators\n"
-                         "def f(): return; yield 1")
-        self.check_suite("from __future__ import generators\n"
-                         "def f(): yield 1; return")
-        self.check_suite("from __future__ import generators\n"
-                         "def f():\n"
+        self.check_suite("def f(): yield 1")
+        self.check_suite("def f(): return; yield 1")
+        self.check_suite("def f(): yield 1; return")
+        self.check_suite("def f():\n"
                          "    for x in range(30):\n"
                          "        yield x\n")
 

Lib/test/test_profilehooks.py

-from __future__ import generators
-
 from test_support import TestFailed
 
 import pprint

Lib/tokenize.py

@@ -22,8 +22,6 @@ are the same, except instead of generating tokens, tokeneater is a callback
 function to which the 5 fields described above are passed as 5 arguments,
 each time a new token is found."""
 
-from __future__ import generators
-
 __author__ = 'Ka-Ping Yee <ping@lfw.org>'
 __credits__ = \
     'GvR, ESR, Tim Peters, Thomas Wouters, Fred Drake, Skip Montanaro'

Lib/types.py

@@ -2,8 +2,6 @@
 
 Types that are part of optional modules (e.g. array) are not listed.
 """
-from __future__ import generators
-
 import sys
 
 # Iterators in Python aren't a matter of type but of protocol.  A large
@@ -83,4 +81,4 @@ EllipsisType = type(Ellipsis)
 
 DictProxyType = type(TypeType.__dict__)
 
-del sys, _f, _C, _x, generators                  # Not for export
+del sys, _f, _C, _x                  # Not for export