Message 85909 - Python tracker

The patch I submitted adds a special-case for inf/-inf/NaN so that
sprintf is avoided for those values.  Should work on any platform, I
believe.

I'm not sure how it interacts with your 3.x plans.  Seems like it would
be a good patch for 2.7 at least, though.

(and the patch that adds tests should go into both 2.7 and 3.x)