Preliminary support for "from __future__ import generators" to enable
the yield statement.  I figure we have to have this in before I can
release 2.2a1 on Wednesday.

Note: test_generators is currently broken, I'm counting on Tim to fix
this.
diff --git a/Lib/tokenize.py b/Lib/tokenize.py
index b79cdc0..cbe4552 100644
--- a/Lib/tokenize.py
+++ b/Lib/tokenize.py
@@ -22,6 +22,8 @@
 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'