[Patches] in-overloading: done right, with Guido's comments folded in (fwd)

[Guido van Rossum]

Thanks, Moshe (and Greg for reviewing).  All checked in!

Request: please submit some testcases for the test suite.  This should
check that (1) a class defining __contains__ now supports 'in'
correctly; (2) a class defining __getitem__ but not __contains__
still works correctly; (3) a class defining neither does not support
'in' and gets a decent error message.

And of course, documentation is still missing.

Two nits:

(1) I couldn't find the checkin messages.  Please refrain from using
phrases like "same checkin message from last e-mail."

(2) Somehow, the patch program got confused by the "---" that you
appended to the end of the patch.  It's better not to use rows of
dashes or starts, since these mean something to the context-diff
recognizer.

--Guido van Rossum (home page: http://www.python.org/~guido/)