Message 96497 - Python tracker

I committed the patch for expm1 in r76861 (trunk) and r76863 (py3k), with 
one small change:  instead of using 2 * exp(x/2) * sinh(x/2), expm1 is now 
computed using a method due to Kahan that involves only exp and log.  This 
seems a little safer, and guards against problems on platforms with a 
naive implementation of sinh.  (I *hope* no such platforms exist, but 
suspect that's wishful thinking. :-)

Thanks to Eric Smith for testing the build system changes on Windows.