There's no need for bootloader on Elbrus platform
since firmware boots Linux just fine; note that
the whole feature is betted omitted since its
script checks for the case when the feature
is requested but not configured properly.

installer-feature-bootloader-$BOOTLOADER dependency of alterator-$BOOTLOADER.
This is necessary so that alterator-$BOOTLOADER is deleted after installation,
if it was not installed explicitly.
This will reduce the minimum installation of alt-server.

This reverts commit 19ed2b9a.

The case at hand was the need to pass serial console parameters,
see the next commit.

$GRUB_ARCHES is the list of GRUB 2 supported architectures

Add target use/bootloader/uboot. Das U-Boot -- the Universal Boot
Loader, used on single board PCs (also in qemu).

Use bootloader lists to provide better portability and to avoid
overcomplicating bootloader switch.

Added restriction for alterator-$$(BASE_BOOTLOADER)) only for
ISO images. Since the new uboot bootloader is not supported in
Alterator and is not used when building ISO images.

This really belongs to bootloader feature rather than
to mixin/desktop-installer alone; moving out.

This one might probably change into core functionality but right now
it should help when you get not the branding, init system, or whatever
alternative you do _not_ need.

See-also: https://bugzilla.altlinux.org/show_bug.cgi?id=30806

...explicitly; this has been triggered by the change to
livecd-install as of 0.9.10-alt2 (doesn't R: alterator-grub
anymore to allow non-grub platforms as well).

This should be a no-op _together_ with the mentioned change
by now as grub is selected explicitly; will take more attention
for e.g. e2k as the problem just shifted here from livecd-install.
Reported-by: Leonid Krivoshein <klark@altlinux.org>

sub/main subprofile should not be requested directly
as documented in its README but rather via use/repo/main;
let's fix this discrepancy and check that no regressions
come hurling down.

This could harm the debug...

Document the one-way nature of bootloader type switching.

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).

These were broken since 5ff375aa10bee7937db457d3df3115f938bb6c77
due to no bootloader being tossed anymore by the very
installer-distro-altlinux-generic (which is the default)

NB: needs installer-distro-altlinux-generic = 6.0-alt2
    as it doesn't require alterator-grub indefinitely