With not-that-recent mkimage-profiles development,
it's no longer apparent that at least a gigabyte
of free space is required to build something useful
(at least for the tests, like syslinux.iso).

In short, the guesser cutoff margin is now 256M.

Just in case the build.log will be inobvious, and it's easy to diagnose
automatically.  Thanks Andrey Stroganov for this use case.

Thanks for improving the initial implementation go to raorn@ for kind
commit lynch and to Yuri Bushmelev for actually suggesting something
more concise.

BTW the "1024" magic number was taken out of thin air:
the "no free space" errors are most likely to happen while
forming/populating a chroot (apt/rpm errors out) and chroots are
roughly two orders of magnitude heftier than a megabyte.

- s/stage2/install2/g
- added pkg/lists
- initial README (ru_RU.KOI8-R)
- mkimage topdir is in image.in/, really (off-tree build)
  + initial bin/mktmpdir
  + BUILDDIR (works)
- s/cd/iso/
- drop --with-distro (considered harmful)