Add proper padding to text section for elf2aout conversion.

The data and bss sections are 8 byte aligned on m68k ELF format,
but a.out header doesn't have section addresses and only
contains size va

Add proper padding to text section for elf2aout conversion.

The data and bss sections are 8 byte aligned on m68k ELF format,
but a.out header doesn't have section addresses and only
contains size values, so we have to pad size of text section
to make data section get aligned even after elf2aout.

Note elf2aout merges ELF data section into a.out text section
if binary is OMAGIC (i.e. text is writable too) so only
BSS section address was affected (and was almost harmless).

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Specify text address via Makefile rather than hardcoding in boot.ldscript.

Revert to using elf2aout(1) to build a.out binary.
a.out binary linked by ldscript doesn't work on some uncertain conditions.

Link the target boot binary as a.out directly rather than using elf2aout(1).
Confirmed working on LUNA-I.

First cut at NetBSD/luna68k native bootloader.

Based on 4.4BSD-Lite2/luna68k "Stinger" loader revision "Phase-31"
http://svnweb.freebsd.org/csrg/sys/luna68k/stand/
and MI libsa glue stuff are taken

First cut at NetBSD/luna68k native bootloader.

Based on 4.4BSD-Lite2/luna68k "Stinger" loader revision "Phase-31"
http://svnweb.freebsd.org/csrg/sys/luna68k/stand/
and MI libsa glue stuff are taken from hp300 etc.

Tested on LUNA-I and old DK315C SCSI disk drive.

LUNA's monitor PROM can load only an a.out binary in 4.3BSD FFS partition
(i.e. created by "newfs -O 0") on disks with OMRON's UniOS disklabel,
but now we can load an ELF kernel in root partition via this bootloader.
(See luna68k/disksubr.c for details of UniOS label)

TODO:
- LUNA-II support (check 68040 to adjust cpuspeed for DELAY())
- secondary SCSI support for LUNA-II
- netboot via le(4) (should be trivial)
- support boot options on bootloader prompt
- bootinfo (passing info about booted device and kernel symbols)
- support "press return to boot now, any other key for boot menu" method
like x86 bootloader (needs cnscan() like functions)
- tapeboot (anyone wants it?)

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