x86: add new page table generation script

This produces a set of page tables with system RAM
mapped for read/write/execute access by supervisor
mode, such that it may be installed in the CPU
in the earliest boot stages and mutable at runtime.

These tables optionally support a dual physical/virtual
mapping of RAM to help boot virtual memory systems.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>