There's a particular problem with lazy evaluation
in case of BOOT_LANG: mkimage uses internal variable,
BOOT_LANG = $(GLOBAL_BOOT_LANG) (note the lack of
immediate assignment there), and if we set up

  export GLOBAL_BOOT_LANG = $(BOOT_LANG)

in the same namespace we end up with recursively
defined pair of variables; a ":=" in either place
would save the day _but_ it's not there in m-p due to
accumulator variables, e.g. USERS, which are defined
and exported by a corresponding feature and then get
populated *after* having been declared for export,
_and_ it's not in mkimage as of 0.2.16 for some reason
that might even be good (I don't know yet).

set() is a function of two variables but the and()
check for *both* is incorrect as one might need to
override a previously set variable with empty string;
this has manifested itself with a case like this:

  @$(call set,ROOTPW_EMPTY,1)
  # ...
  @$(call set,ROOTPW_EMPTY,)

A few too many downstream makefiles employed the pattern
of "export GLOBAL_VAR := $(VAR)"; macroize that.

bin/ prefix tried to become a permatemp(tm).  No way.

Initial openSUSE package base taming effort has shown that
relatively few things should be fixed; subst has been generalized
as -i option to sed(1) since its introduction, so let's just fix it.

The features might get copy-pasted (or even copied-and-pruned)
when initialized; there's an unneccessary duplication of the
function name in the line adding it to FEATURES list, thus
prone to being forgotten and causing some havoc later on.

It was wrong in the first place but tackling this with some
double-colon rules ran into terminality issues, and further
tortures were considered unneccessary.

The current solution isn't perfect (no completely transparent
function name registration upon corresponding target being called)
but at least it is an improvement...

This is quite a large-scale change since mkimage-profiles got used to
baking distributions over the last year, and virtual environments are
quite different, so e.g. image.in/Makefile had to be split in two with
the main part of it moved into features.in/iso/lib/.

Short overview:

- features.in/Makefile: lib/ support
  (supporting VE images requires dynamic modifications
  to image.in/Makefile before starting the build;
  the most natural way to achieve that seems to use
  features mechanism along with makefile include dir)

- packaging format related part moved into features.in/pack
  (should be better prepared for diversity either)
- features.in/iso renamed to features.in/build-distro
- features.in/ve  renamed to features.in/build-ve
  + NB: these could not be merged as e.g. features.in/build
    due to completely different script hooks

- lib/image.mk renamed to lib/build.mk
- image, config, log postprocessing moved downstream
- added a sort of a topping in the form of lib/sugar.mk
- assorted style fixups (like ifeq usage)

- clean.mk: reliability fix (the problem was observed by Oleg Ivanov
  and me too but finally it did get the attention quantum)

- reviewed, updated and extended docs
  + QUICKSTART: should be[come] a step-by-step guide
    (thanks Leo-sp50 for prodiving feedback)

Applying set() and only set() to a GLOBAL_* is safe
but still a potentially confusing example; so let's
just do it right (and warn unsuspecting folks too).

Now we don't dump all the gory details onto thee
but rather log them handsomely and present only
the most important details by default; use DEBUG=1
and/or BUILDLOG=/path/to/file to tweak.

Also introduced IMAGEDIR and IMAGENAME.

The rest:
- ovz-smp is no more
- base-l10n pkglist (suggested by Alexander Kuprin)
- clean.mk:
  + fixed an oversight: the test result erroneously applied
    only to the first command of several ones that should be
    run iff build/ is a symlink
  + drop implicit rules (it's no C code)
- Makefile: more reasonable iso names
- image.in/Makefile: .disk/date too

- more thorough build stages inline doc
- quieter BUILDDIR instantiation
- branding-altlinux-sisyphus by default
- prettify installer selection somewhat
- mkimage #24669 fixed upstream
- sub.in/stage1/modules: +drm (as in m-p-d, for KMS)
- tags2lists: generalize a bit

- drop hardwired kernel flavour from pkglists
- today's std-ng lacks aufs, let's switch to un-def
- second assault at KERNEL_PACKAGES_REGEXP
- re-introduced kpackages (builds ok)

PS: base lists: switch to grub, add udev, cleanup

tags2lists was tweaked to work on the more natural word boundaries
than explicit "_", and the lists were renamed accordingly.

Dropped the borrowed pkglists by the way.

A major change in approach largely thanks to discussions
with Alexey Cheusov but also well aligned with my own findings:
autoconf doesn't let the variables to form an inheritance.

And data flow described at http://www.altlinux.org/WhiteLabel
(which in its turn was born thanks to Gavin Henrick of Diva Telecom
and to Alexander Bokovoy of SaM-Solutions) is really dependent on
the existence of such an inheritance.

Also:
- distro.mk += try()
- "hide" special targets
- fixed wrt distro/.{base,init,metaconf}, thx gns@
- README updates
  + added metaconf.mk
  + clarifications
- updated pci.ids location for hdt

Also included:
- reworked syslinux feature inclusion
- syslinux: s/textprompt/prompt/
- README++

- set(), add(), log()
  + special thanks to rider@ for log format feedback
- simple debug facility
- builds, installs and runs... again