Reinstate INSTALL kernel for embedded ramdisk installs.

Reasons being:
- INSTALL is GENERIC with an embedded ramdisk, and as such, can benefit from
features included within.
- INSTALL_FLOPPY has its own config(5) file, and is tailored for "small"
floppy images; it misses features/drivers that could be needed to boot
in a decent environment for recent x86 machines (like ACPI)
- makes it closer to floppies distrib available for amd64

While here, comment out INSTALL_FLOPPY and bootfloppy-big image build. NetBSD
does not use the 3.6MiB image for El Torito cdroms anymore.

Remove the FLOPPYMAX limit; i386 needs 4 floppies now. Modify boot.cfg and
release/contents to reflect reality.

See http://mail-index.netbsd.org/port-i386/2011/02/08/msg002307.html

No comments, no objections.

branches: 1.12.2;
The XEN2 kernels are no more.

branches: 1.11.6;
Put the GENERIC kernel onto i386 installation CDs and load a kernel module
from the boot loader to provide the miniroot.

For PR kern/38537:

- Make MULTIPROCESSOR mandatory on i386.

Installation changes:

- Update installation section of release notes to match reality.
- Rename INSTALL to INSTALL_FLOPPY, retire INSTALL_LARGE.
- Build INSTALL kernel from GENERIC, like on amd64.
- Update boot menu to allow disabling ACPI and/or SMP.
- Remove GENERIC.NOACPI from the installed kernel list.
- TODO: install default boot.cfg in etc.tgz.
- TODO: possibly enable PCI fixup stuff at runtime if ACPI is disabled.

Build changes:

- No longer build ALL, it's for verification, is slow to build and the
build process is already crippled by the number of kernels built.
- No longer build GENERIC.NOACPI.

branches: 1.9.2; 1.9.6; 1.9.8;
build XEN3PAE kernels as part of release.

Remove GENERIC_LAPTOP and INSTALL_LAPTOP. To compensate, switch
bootfloppy-big to actually use INSTALL_LARGE (with ACPI) and 5 floppies.

branches: 1.7.4; 1.7.6;
Add a comment reminding to update the release documentation when the
list of released kernel images change.

For the benefit of modern hardware, enable ACPI by default in INSTALL and
GENERIC kernels. If ACPI is an issue on your hardware, 'boot -c' and
'disable acpi' should be a workaround. ACPI-enabled kernels works fine
on pre-acpi hardware.
for amd64:
- add ACPI to INSTALL and GENERIC, remove the *_ACPI config files.
- get rid of the bootfloppy-big.fs boot image, and got to a 3-floppy boot
image
for i386:
- introduce INSTALL_LARGE which has ACPI and some devices with big firmware
- move some devices from INSTALL to INSTALL_LARGE
- Boot floppies still use INSTALL, and bootfloppy-big.fs is still there
(for thoses who want to build el-torito floppy emulation boot CD) and use
INSTALL.
For both, drop the 'iso-image' code in etc/ to make the iso bootable, we'll
use something else to build bootable CDs.

branches: 1.5.2;
As has been pointed out recently, the list of i386 release kernels needs
updating. Probably to an ACPI kernel that need not fit into an 'emulated floppy'
and a 'legacy' kernel that will fit.
In any case the small/tiny kernels which are really for i386 systems with
< 16MB of memory (some are sized for a 5.25" floppy) don't need to be built.
Remove bootfloppy-small, bootfloppy-tiny, rescue-tiny and bootfloppy-ps2
and associated ramdisks.

Do not strip INSTALL kernels. Makefile.tarfloppy does this now.

Don't strip (and don't generate the symbols.gz files) for Xen INSTALL kernels.
There's no space contraint here, and this makes debugging easier.

Rename XEN kernel config files to be more consistent:

INSTALL_XEN3_U -> INSTALL_XEN3_DOMU
INSTALL_XENU -> INSTALL_XEN2_DOMU
XEN0 -> XEN2_DOM0
XEN3_U -> XEN3_DOMU
XENU -> XEN2_DOMU

OK'd by bouyer@

Prepare creation of boot CDs:

* Move files in distrib/i386:

floppies/instkernel/Makefile -> instkernel/Makefile
floppies/ramdisk-big/Makefile -> ramdisks/ramdisk-big/Makefile
floppies/ramdisk-big/disktab.preinstall -> ramdisks/ramdisk-big/disktab.preinstall
floppies/ramdisk-big/list -> ramdisks/ramdisk-big/list
floppies/ramdisk-big/list.inet6 -> ramdisks/ramdisk-big/list.inet6
floppies/ramdisk-rescuetiny/Makefile -> ramdisks/ramdisk-rescuetiny/Makefile
floppies/ramdisk-rescuetiny/list -> ramdisks/ramdisk-rescuetiny/list
floppies/ramdisk-small/Makefile -> ramdisks/ramdisk-small/Makefile
floppies/ramdisk-small/list -> ramdisks/ramdisk-small/list
floppies/ramdisk-tiny/Makefile -> ramdisks/ramdisk-tiny/Makefile
floppies/ramdisk-tiny/list -> ramdisks/ramdisk-tiny/list
floppies/common/Makefile.ramdisk -> ramdisks/common/Makefile.ramdisk
floppies/common/dot.profile -> ramdisks/common/dot.profile
floppies/common/list.ramdisk -> ramdisks/common/list.ramdisk
floppies/common/termcap.mini -> ramdisks/common/termcap.mini

* Adjust paths