This patch adds toplevel profiledbootstrap.

Since this makes stage1 have multiple descendants, I had to abandon
the prev/next scheme to link bootstrap-stages.

Instead, I either specify dependancies separately or use double-colon
rules, which allowed commands to be defined (using prev) while the
[+FOR+] has reached the successors of a stage.  This should be portable,
but I'm afraid it falls under the "may turn out to be unmaintainable"
axe.  What do you think?

Ok for mainline/src?

Paolo