Make $($(var):J=x) join the multiple values of var.
Previously,
it only the elements of individual value.
=== computer.perforce.com:1666: Change 20731 by seiwald@spice on 2001/02/19 23:04:05
Hmmm. Given the (garbled?) description above, and after looking
at the code, and trying experiments, I'm unsure just _what_
the previous bahavior had been; but since :J was previously
unreleased, Lets just consider this a fix to an unreleased bug,
and leave it undoc.