8086 boot code

Code in the following blocks assemble into a binary that is
suitable to plug into Core words (B350) to achieve a fully
functional Collapse OS. It is structured in a way that is
very similar to Z80 boot code (B280) and requires the same
constants to be pre-declared.

RESERVED REGISTERS: SP is reserved for PSP, BP is for RSP and
DX is for IP. Whenever you use these registers for another
purpose, be sure to protect their initial value. Like with
Z80, you can use SP freely in native code, but you have to make
sure it goes back to its previous level before next is called.


                                                        (cont.)