...unless we're debuggin'.

Overview of the changes:
- ARM support: separate ext2 /boot, no LILO
- avoid race condition with devmapper
- trap ERR so that -e in shebang doesn't result in extra cleanup hassle
- configurable root filesystem type (ext4 by default)
- jumps through parted hoops

Details:

1. LILO is x86-specific while the rest of the script can be used
   to prepare e.g. Marvell ArmadaXP or CuBox images; we can generally
   count on uboot supporting ext2 for relatively sane platforms but
   not ext4 that would be a better root filesystem performance-wise.

2. Apparently /dev/mapper/loopXpY can be still missing at the time
   when kpartx returns and pop up a bit later... sit there, wait
   and check for it.

3. If something went wrong with any command of the script it would bail out
   due to -e in shebang; it is now better to clean up the loopback device
   and its mappings in this situation either.

4. One size doesn't fit all, really.

5. The parted sizing was sloppy as in broken, now it's just half insane.
   Someone's decision to stick units and auto-alignment knobs into
   a single one was apparently hilarious...

   http://www.gnu.org/software/parted/manual/parted.html#unit

Manual loop/dm cleanup is described in documentation just in case.

/boot size meter is suboptimal in terms of additional I/O incurred,
will be most likely rewritten to make use of advance "du -s".

The feature officially introduces the "engineering passwords"
including empty ones which have been around since forever but
weren't properly managed (and still are not, at least until
there are no stray passwd/chpasswd/usermod calls in both the
profile, installer-features and all the other related parts).

It is based on an m-p-d init3-users script by stanv@ but was
cleaned up and restructured in a pretty severe manner; thanks
glebfm@ for additional discussion.

This also cleans up the kludge previously stuck into build-vm.

Note that vm/icewm sports graphical autologin now as well as
the default root password (which can be overridden by passing
ROOTPW=... to make but it is a change from the previous state
of affairs indeed).

Classic VEs don't carry any kernel since these are running
under a single OpenVZ (or potentially LXC) kernel image;
ARM Multiboot (TWRP in this particular case) allows to boot
off a chroot via kexec, and we need a kernel in it for that,
obviously.

No bootloader required inside such VE though.

There was some extra duplication, just clean it up.

mkimage implementation requires that the variables
to be passed to the scripts are to be prefixed with
GLOBAL_ or INFO_ tags as appropriate; in this case
the upstream makefile didn't care to.

It's better to rather just move the raw image instead
of specifically converting it into the same, and there's
no need for qemu-img altogether then.

Let's drop the intermediate raw image after successful
conversion as well.

A virtual machine isn't very useful if there are no means
to access it; let's bring up the basic networking and provide
root SSH access via pre-existing public key.

As the remote access with known default credentials is roughly
equivalent to just lending one's VMs to anyone with network
access to it, the fallback root password is now exterminated;
you have to provide one (or a long enough random string
if you plan to use keys only, see e.g. apg utility).

Raw disk images are convenient and universal
but there are custom formats like Qemu's qcow2
providing additional features, e.g. copy-on-write
or space savings.  All of this ultimately belongs
to mkimage but in the mean time has been implemented
here as well.

Yes, mkimage-profiles is now able to build VM disk images.
So far the support is pretty basic:

- a single hard drive image with a single partition/FS
- only stock root password is configurable
- LILO is hardwired as a bootloader

The resulting images tend to boot under qemu/kvm though.

Please see doc/vm.txt for the warning regarding additional
privileges and setup required.  This was started back in
February but I still hoped to avoid sudo/privileged helper
(and libguestfs is almost as undistributable as can be)...

Thanks:

- http://blog.quinthar.com/2008/07/building-1gb-bootable-qemu-image-using.html
- Alexey Morarash who reworked that as https://github.com/tuxofil/linsygen
- led@, legion@, vitty@, aen@ for providing advice and inspiration