- New __PA() macro for physical address.
- Rename pg0 to more descriptive boot_pgtables.  Remove unused pg1.  Add 
boot_pgtables_end instead of relying on empty_zero_page.
- Don't hardcode pte entries in swapper_pg_dir.  Let the linker do its job.

This is in preparation to move empty_zero_page, swapper_pg_dir, and 
boot_pgtables to other data sections.

--
				Brian Gerst