Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Remove unused variables.

Since the BAT mapping was removed a long time back, it can't
be assumed that modules are contiguous in memory (they're not)
so don't blindly __syncicache start/end. In fact, don't bother
syncing the icache for modules since the kernel will do it after
fixing up relocations.

This fixes the trap when loading modules at boot time.

Reported by: orlando at break dot net

Extract entry point from elf header before releasing the heap.
This caused a data-miss trap when the BAT init code was removed
on PPC.

Compile tested on: panther (sparc64). Code built, but not used, on sparc64.

Convert to __FBSDID.

Make __elfN(ofw_loadfile) match parameter declaration for file_format
in boot/common/bootstrap.h. Having a 32-bit size when a 64-bit param
is declared wreaks havoc on PPC.

Not objected to by: sparc64

Enable the i386 loader to load and run an amd64 kernel. If this puts
things over floppy size limits, I can exclude it for release builds or
something like that. Most of the changes are to get the load_elf.c file
into a seperate elf32_ or elf64_ namespace so that you can have two
ELF loaders present at once. Note that for 64 bit kernels, it actually
starts up the kernel already in 64 bit mode with paging enabled. This
is really easy because we have a known minimum feature set.

Of note is that for amd64, we have to pass in the bios int 15 0xe821
memory map because once in long mode, you absolutely cannot make VM86
calls. amd64 does not use 'struct bootinfo' at all. It is a pure loader
metadata startup, just like sparc64 and powerpc. Much of the
infrastructure to support this was adapted from sparc64.

Major rework of how we copy data into kernel space.

We now talk to the memory and mmu instances directly rather than using the
OpenFirmware "claim" method.

Add support for passing metadata.

#if 0 more bootinfo stuff.

Add new files needed by previous commit.