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

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

Fix some memory management issues discovered when trying to boot the PPC
OF loader on systems where address cells and size cells are both 2 (the
Mambo simulator) and fix an error where cons_probe() was called before
init_heap() but used malloc() to set environment variables.

MFC after: 1 month

Remove unused variables.

Start each of the license/copyright comments with /*-

G5 support: handle the case where the OpenFirmware memory array uses
64 bits for the phys address, but only 32 for the virtual address.

Convert to __FBSDID.

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.

Make the ofw_reg structure and ofw_alloc_heap 64-bit save.

Add new files needed by previous commit.