Get the toolchain able to build 64-bit PowerPC FreeBSD binaries.

Obtained from:	\\depot\projects\ppc-g5
Set INLINE_LIMIT for ppc64. Now, with some symlink hackery, a kernel build
for TARGET_ARCH=ppc64 will actually start. Of course, it will not
complete...
Before I get too far, rename the architecture from 'ppc64' to 'powerpc64'.
This seems to be a more common name.
Add some #ifdefs to powerpc _types to set LP64 types if we are compiling
for 64-bit PowerPC. The goal here is to share machine/*.h completely
between powerpc and powerpc64.
Add in some more type-dependent definitions and define 64-bit atomic
functions on powerpc64. This (a) manages to not break a 32-bit kernel
and (b) gets all of the MI stuff in the 64-bit kernel compiling. The
elf.h changes are a hack and should be revisited after a closer look at
the 64-bit ABI.
Add separate powerpc64 conf files for now and remove an extraneous include
of opt_psim.h from aim's nexus. I'm a little torn on how much architecture
unification there should be here.
This gets the rest of the shared AIM code building for AIM64. Most of the
changes are adjusting printf formats and setting things that should be
register_t to register_t.
Checkpoint current status: everything currently compiles except
aim/copyinout.c, powerpc/elf_machdep.c, and powerpc/in_cksum.c. Hopefully,
I will see some hello world boot messages soon.

Changes are:

- Create a new powerpc/aim64 directory to hold a small number of
  aim64-specific files. Depending on whether we need to have a
  sys/powerpc64 in the end, this could be moved there.
- Move aim/mmu_oea64.c to aim64
- Pacify the compiler about changed types, update trap_subr.S, etc.
- Remove device options for devices that don't exist on any PPC64
  machines.
Fix a segfault in ld when the PLT is defined but not used. This follows a
similar change in 2006 made by Alan Modra.
Add powerpc64 bits for xlint. This allows make kernel-toolchain to complete.
Add bits for generating 32-bit PPC binaries.
Add in some more missing bits, and a few beginning corrections for the
dot symbol function descriptor business in the PowerPC64 ABI. This produces
a kernel that compiles, links, and even manages to make it into
powerpc_init().
Add the various OFW machdep bits to be able to talk to a 32-bit Open
Firmware from a 64-bit environment, and also to handle calling locations
in memory from C. This involved hacking a PPC64 ABI function descriptor
structure to wrap the plain pointer to the OFW entry point.

With this, the kernel starts, prints Hello World, starts KDB, informs me
it has no platform module because the Mambo support is uncommitted,
politely panics, and stops. Huzzah!
Fix a missing space.
Bring up the system a little more, with some initial SLB management. We now
boot into after the PMAP layer is up and the MMU enabled.
Virtual memory now really works, and the kernel boots to the point of
running through device detection and complaining about not being able
to find a PIC. Trap handling (especially for user-space) still has a
ways to go.
The correct opcode for reading the console is 60, not 0.
Fix physical memory map detection on IBM-style machines like the
Cell simulator.
Fix 32-bit build.
Make 32-bit kernels operational again by not storing DAR and R31 in the
same part of the register cache for traps, and by dealing with some
stupidity in the way Apple stores the available physical memory list
in firmware.