Here's a patch incorporating Christian's tests, the missing lines from 
PyObject_RichCompareBool, and some additional tests to check that
[x] == [x] and the like remain True even when x is a NaN.  Oh, and a 
Misc/NEWS entry.

With this patch, all tests pass (debug and non-debug 32-bit builds) on OS 
X 10.5/Intel.

I think we should get the okay from Guido before committing this.  Maybe 
he remembers why he deleted these lines in the first place. :-)