Split rombios32.c up into multiple files.

Review changes committed to coreboot, virtualbox, qemu, kvm, and bochs
cvs tip.

Look into ways to reduce stack usage.  Alter ISRs so that they do not
enable irqs.  Only call out to other bios functions after minimizing
stack usage.

Audit all sti/cli calls.  Audit all call16 calls to make sure flags is
setup properly with respect to irqs.

Audit statements where a 32bit intermediary changes meaning of a 16bit
comparison.

Code assumes ebda segment is static - it doesn't read 0x40e.

The __call16 code does a long jump to the interrupt trampolines - this
is unnecessary.

Fix makefiles so that they rebuild the required files automatically.

Cleanup setting of ES on GET/SET_BDA

Possibly implement 32bit pcibios support.

Allow one to select adding 32 bit code to 0xf000 or in a separate
location.

Try generating bios tables at compile time.

Move e820 map generation to post time (just have e820 code copy pre
made tables back to user).