will backport.

guess_all_extensions() returns (at least) what we expect.  As Jeff
Epler suggests in

http://mail.python.org/pipermail/python-dev/2003-September/038264.html

We use a set to test the results.  This fixes the test when
test_urllib2 is run before test_mimetypes.

If some other test comes along and uses mimetypes, it will be
initialized from the system files.

there are no matching types.  Updated the docs and docstrings.  Added
some unit tests.

imports e.g. test_support must do so using an absolute package name
such as "import test.test_support" or "from test import test_support".

This also updates the README in Lib/test, and gets rid of the
duplicate data dirctory in Lib/test/data (replaced by
Lib/email/test/data).

Now Tim and Jack can have at it. :)

non-standard but common types.  Including Martin's suggestion to add
rejected non-standard types from patch #438790.  Specifically,

guess_type(), guess_extension(): Both the functions and the methods
grow an optional "strict" flag, defaulting to true, which determines
whether to recognize non-standard, but commonly found types or not.

Also, I sorted, reformatted, and culled duplicates from the big
types_map dictionary.  Note that there are a few non-equivalent
duplicates (e.g. .cdf and .xls) for which the first will just get
thrown away.  I didn't remove those though.

Finally, use of the module as a script as grown the -l and -e options
to toggle strictness and to do guess_extension(), respectively.

Doc and unittest updates too.

allows using the tests with unittest.py as a script.  The tests will
still run when run as a script themselves.