These changes allow you to create two independent config at the same
time or separately. It will be possible to add support for grub-pc in
the future.

The scripts were named the same for syslinux and grub. Because of this,
scripts for syslinux were overwritten by grub scripts.

It's not exactly obvious how install2_size, live_size or rescue_size
get defined since the variable names themselves get constructed;
help git grep these down.

There's much reason for reuse instead of duplication
among the different stage2-based subprofiles.

In particular, the rather monolithic driver cleanup script
of the ancient is better done in several clear pieces with
the final depmod run.

Scripts dropping apt/rpm databases will dump pkglist first.

A script purging /boot/* will honour live-install if present.

Minor inno^Wfixups all over the map too.

Implementation based on m-p-d::profiles/scripts.d/03-syslinux
(but heavily modified for m-p of course)