If POST is rerun, try to do a machine reboot.

Review changes committed to coreboot, virtualbox, qemu, kvm, and bochs
cvs tip.
  * bochs cvs (20100104):
    -- changes synched
  * coreboot (r3348):    (bochs 20060708)
    -- no noteworthy enhancements
  * qemu - now uses SeaBIOS
  * kvm - now uses SeaBIOS
  * virtualbox (r13560): (bochs 20061231)
    -- lots of mouse changes, logo, scsi/etherboot hooks,
       floppy data rate?, int19 calls post

Possibly move code from entry_post in romlayout.S to C code in
handle_resume and always call 16bit C code on post.

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

Support PCIv3 roms?  Add support for PCI "configuration code"
extensions?

Possibly add option to eliminate tsc based delays on emulators.

Add a kconfig style configuration program instead of requiring users
to modify config.h.

Possibly support sending debug information over EHCI debug port.