Default merged to stable for 4.0.0 release

[John W. Eaton]

I've merged default to stable in preparation for the 4.0.0 release.

Changes that are appropriate for the release should go on the stable 
branch.  This includes fixes for serious bugs and regressions only (but 
if they are invasive changes, we should discuss first).  At this point 
it is still OK to introduce backwardly incompatible changes.  Once the 
4.0.0 release is made we will expect changes on stable to preserve 
binary compatibility for all 4.0.x release.

All other changes should be made on default.

jwe