CVS branch switch

[Stephen Weeks]

> It doesn't look like anyone's tried to fix what I did, so I am about to start.
> I'll send mail when I've succeeded.  It's best not to make any other CVS changes
> in the interim.

OK.  I believe I've fixed my mistake.  Sorry about that.

There is now a tag, ssa-root, that identifies the point at which the ssa branch
attaches to the trunk, and a branch tag, ssa-branch, that identifies the current
tip of the ssa branch.  These tags currently point at the same set of file
revisions, but that will change as soon as Matthew and I start fixing the bugs.

Suresh, if you want to see the SSA IL, you can do
	cvs co -r ssa-root
and have a look at mlton/ssa/ssa-tree.sig.

Please feel free to resume using CVS.  Again, sorry about the mixup.