bootxx_cd9660 (cdboot), like bootxx_fat16 (fatboot), is not a traditional
libsa-based program. As such, build bootxx_cd9660 where its source lives.
This has been done by moving bootxx/bootxx_cd9660/Makefile to cdboot/Makefile
and adjusting the relative paths appropriately, so as to minimize binary change.

Build and install bootxx_ext2fs, primary boot for ext2fs.

Ext2fs doesn't have enough free space (it has only 1KB)
to store this primary loader, but we can put it into
an independent small 'boot' partition as NetBSD/hp300 does
if it's really necessary.

It could be a fun project to add smaller pre-primary loader
that loads ~8KB primary loader for ext2fs, but probably it's unlikely
because there is a functional wheel named GRUB for ext2fs.

Introduce .WAIT into the cleandir rule for blasting the libsa/libkern/etc.
trees, because it can race with the libsa/libkern/etc. makefiles' own
cleandir rules. I think I've found all of the uses of the offending idiom...
Closes PR 43360.

branches: 1.11.56; 1.11.70; 1.11.76; 1.11.78;
use "=" instead of ":=" where .OBJDIR is used because it might change
later in <bsd.obj.mk>, thanks to Alan Barrett for the hint

branches: 1.10.20; 1.10.22;
merge ktrace-lwp.

Ensure we don't build the libraries twice: move the .WAIT after
the first subdirectory that uses the libraries. That subdirectory
is bootxx_ffsv1, not bootxx_cd9660.

Build and install /usr/mdec/bootxx_cd9660, a primary boot loader
for ISO9660 filesystems.

branches: 1.7.12;
Need to use := when evaluating ${.OBJDIR}, then the correct value
is passed into the subdir builds and the 'lib' objects are correctly shared.
Fixes PR/26554

Add .WAIT after first subdirectory to ensure we don't build the libraries
twice.

Add bsd.obj.mk so these directories get their own obj directory (for the
library objects shared by their subdirectories).
Needed when the obj directory isn't a parent of the subdirectories obj directory

Change the way the shared lib directory is handled.
Should now work if ${.OBJDIR} = ${.CURDIR}/obj.

Overhaul MBR handling (part 1):

<sys/bootblock.h>:
* Added definitions for the Master Boot Record (MBR) used by
a variety of systems (primarily i386), including the format
of the BIOS Parameter Block (BPB).
This information was cribbed from a variety of sources
including <sys/disklabel_mbr.h> which this is a superset of.

As part of this, some data structure elements and #defines
were renamed to be more "namespace friendly" and consistent
with other bootblocks and MBR documentation.
Update all uses of the old names to the new names.

<sys/disklabel_mbr.h>:
* Deprecated in favor of <sys/bootblock.h> (the latter is more
"host tool" friendly).

amd64 & i386:
* Renamed /usr/mdec/bootxx_dosfs to /usr/mdec/bootxx_msdos, to
be consistent with the naming convention of the msdosfs tools.

* Removed /usr/mdec/bootxx_ufs, as it's equivalent to bootxx_ffsv1
and it's confusing to have two functionally equivalent bootblocks,
especially given that "ufs" has multiple meanings (it could be
a synonym for "ffs", or the group of ffs/lfs/ext2fs file systems).

* Rework pbr.S (the first sector of bootxx_*):
+ Ensure that BPB (bytes 11..89) and the partition table
(bytes 446..509) do not contain code.
+ Add support for booting from FAT partitions if BOOT_FROM_FAT
is defined. (Only set for bootxx_msdos).
+ Remove "dummy" partition 3; if people want to installboot(8)
these to the start of the disk they can use fdisk(8) to
create a real MBR partition table...
+ Compile with TERSE_ERROR so it fits because of the above.
Whilst this is less user friendly, I feel it's important
to have a valid partition table and BPB in the MBR/PBR.

* Renamed /usr/mdec/biosboot to /usr/mdec/boot, to be consistent
with other platforms.

* Enable SUPPORT_DOSFS in /usr/mdec/boot (stage2), so that
we can boot off FAT partitions.

* Crank version of /usr/mdec/boot to 3.1, and fix some of the other
entries in the version file.

installboot(8) (i386):
* Read the existing MBR of the filesystem and retain the BIOS
Parameter Block (BPB) in bytes 11..89 and the MBR partition
table in bytes 446..509. (Previously installboot(8) would
trash those two sections of the MBR.)

mbrlabel(8):
* Use sys/lib/libkern/xlat_mbr_fstype.c instead of homegrown code
to map the MBR partition type to the NetBSD disklabel type.


Test built "make release" for i386, and new bootblocks verified to work
(even off FAT!).

branches: 1.2.2;
Remove "lib" directory in "cleandir" target.

bootxx: bootstrap code - installable by MI installboot.
Loads /boot using filesystem accesses (rather than a list of block numbers)