Complete six.moves #66

There are a bunch of six.moves submodules (and other things) that aren't supported yet because there are no stubs yet for the module to which they refer. We should remember to update six.moves whenever we add stubs for such a module.

References:

• Unmerged PR that added everything: Add third-party six package #21
• Merged PR that added only those items that work: Add stubs for some of the most heavily used parts of six.moves  #61
• Issue with a list of things to do: Help wanted: stubs needed for six.moves #22
• Tool that generated the initial PR (I think): https://github.com/o11c/stubtool