32bit UID support in 2.3.39

[Roland McGrath]

I would agree with Mark here, that 2.1.3 (which is already on the doorstep)
should go out without these changes.  If they are in fact so stable, then
2.1.4 can go out with them in not too long.  But we need 2.1.3 out asap
without any new ghost of a chance of incompatibility or instability.
This doesn't need to be such a big deal if we just push the bug-fix releases
out more often when we have stable bug fixes, and keep them really "bug-fix".

To my mind, any interface changes at all (even with versioning) going into
2.1.x at all need to be very strongly justified; I'd prefer to see this
wait for 2.2.