First part of the "what version of CURRENT" fix.

We now have RELEASE=CURRENT in the CVS-tree.

If this hasn't been edited, we will use "BUILT-yyyymmdd" where the time is
that of the compile, and leave it at that, we can't do any better.

If there is no serious objections, I will modify the "cvs co" script on
freefall to fiddle this file after checkout so that it becomes
CURRENT-yyyymmdd, where the time is that of the checkout.