Make RELDATE be on a single line.

All variable assignments that start in column 1 have to be on a single
line for amd to build due to as weird dependency there (most likely it
can be fixed to use the new VARS_ONLY feature, but it isn't
today). usr.sbin/amd/include/Makefile calls
usr.sbin/amd/include/newvers.sh which does:
eval LC_ALL=C egrep '^[A-Z]+=' $1 | grep -v COPYRIGHT
which is where that requirement comes from. It handles COPYRIGHT since
that's an exception. Rather than add additional exceptions, cope with
the long line in newvers.sh instead. Note: it no longer needs to
filter COPYRIGHT because the assignment doesn't start in column 1
anymore.

I had done a universe when I had an earlier version of r346018 that
had it as one line. When I changed it to multi-line as suggested in
the review, I only built kernels on a couple of architectures to make
sure it didn't break anything.

Add comment to newvers.sh noting this.

Obviously, this unbreaks the amd build.