[Python-Dev] Add -3 and -Wd to the buildbots

Hi, now that the py3k warnings are fixed (see http://bugs.python.org/issue7092) we should run the tests on the trunk buildbots with the -3 flags, in order to check if new warnings are introduced and possibly to uncover other ones. It might be a good idea to add the -Wd flag too, both on trunk and py3k. -Ezio