With a vote and a half in favor, I'll go ahead with this probably later today.  There is one change needed to the `clean` script; the `hg purge` call should ignore Lib/test/data to avoid downloading the codecmaps test files every time.  I may backport to 3.4 and/or 2.7 later on, but will not do so until default has been happy with it for a while.

I'll leave buildmsi.bat in place for now; I'm interested in trying to resurrect the daily MSI builder some day.  Possibly not before Steve converts us to WIX :)