run manual apt-get update to pick up the latest py3 security update

required for windows compilers

to do that fix a missing $DIST variable usage in the test script

during bootstrap eatmydata is not available in the chroot so it takes a
significant time. Avoid this by placing the whole chroot in a tmpfs
ramdisk.

adds 32 bit and debug tests.

Works with Python 3.x now that bdist_mpkg is ported (thanks @matthew-brett).

Run the 2to3 ws_comma fixer on *.py files. Some lines are now too long
and will need to be broken at some point. OTOH, some lines were already
too long and need to be broken at some point. Now seems as good a time
as any to do this with open PRs at a minimum.

Now is as good a time as any with open PR's at a low.

These scripts have been broken for years (build.py errors out
immediately if not running from an *svn* checkout), so I'm sure
no-one's using them, and they only attract pointless maintenance fixes
(py3 changes, keeping the pointless extra copy of the top-level
README.txt up to date as in #3288). Let's just remove them.