testing cleanup

testing

fix again() bug in demo

minor fix to argv support

Add sys.argv support for demos.

Demo fixes, see changelog

New demo class, very handy for interactive presentations.

Revert Shell.py changes, they don't work.

Minor fixes in genutils, and a BIG fix for threading. I _think_ I got Ctrl-C to work in the threaded shells, and the solution is in fact absolutely trivial. The new code is _much_ simpler than what we had! This needs testing, because I find it almost hard to believe that we hadn't tried this before. But if it works, great! The only limitation is that in threaded mode, the traceback shows the internal sigint handler frame. Big deal, it's just cosmetic.

Fix extra newlines in autocalling.