Add the NannyNag exception class and the process_tokens() function to

__all__, to indicate these are implied as part of the public API.

IDLE's "Check Module" command uses this, and it broke once already
because the reset_globals() and tokeneater() functions were deleted
when Neil converted this to using the generator API of tokenizer.
(See SF bug #448835.)

Lib/tabnanny.py

@@ -17,7 +17,7 @@ import tokenize
 if not hasattr(tokenize, 'NL'):
     raise ValueError("tokenize.NL doesn't exist -- tokenize module too old")
 
-__all__ = ["check"]
+__all__ = ["check", "NannyNag", "process_tokens"]
 
 verbose = 0
 filename_only = 0