Make use of the W atomic rule optional, so that I can talk about its
effects.
Various tweaks aimed at reducing the bubble log defect.
Make it easy to turn off the self-racing checks, for testing.
Tweak delays in the test harness a little.
Try to discourage make from blowing away intermediate files which take
a long time to generate.
Slightly better complex_alias test.
Fix a compiler warning.
Fix another compiler warning.
Fix yet another compiler warning.
Much better complex aliasing test.