Allocate high memory out of the way to hold the shuffle descriptors,
and generate continuation descriptors as needed.

The shuffle and boot interface, including the library support, should now
work as advertised.  Add an ELF-loading module as a demo, and it's probably
useful for someone, too.

Initial checkin of a wrapper infrastructure for the "shuffle and boot"
interface, both real and protected mode.  This code automatically will
figure out the necessary sequence of moves, taking into account swaps
and overlaps as necessary.