Things to do to tinytest

o Replace the license with something recognizeable
o Test forking on win32.
o Write minimalist libevent-legacy thing.
o port libevent tests; move libevent test main into a new regress_main
o allow per-group forks.
o See where we're at.

- Allow groups to nest, perhaps.
- Port Tor to use tinytest
- Warn when running multiple tests with --no-fork
