Move 8086 boot code from B800 to B440

That slims down blkfs a lot.

blk/001

@@ -7,6 +7,5 @@ MASTER INDEX
 170-259 unused                260 Cross compilation
 280 Z80 boot code             350 Core words
 410 PS/2 keyboard subsystem   420 SD Card subsystem
-440-519 unused                520 Fonts
-550-799 unused
-800 8086 boot code
+440 8086 boot code
+470-519 unused                520 Fonts

blk/441

@@ -10,4 +10,4 @@ size of stack. This allows for some interesting optimization.
 For example, in SWAP, no need to pop, chkPS, then push, we can
 chkPS and then proceed to optimized swapping in PS.
 
-To assemble, load blocks 805 through 820.
+To assemble, load blocks 445 through 460

doc/usage.txt

@@ -109,12 +109,9 @@ try to strive towards a few goals:
 1. Block 0 contains documentation discovery core keys to the
    uninitiated.
 2. B1-B4 are for a master index of blocks.
-3. B5-B199 are for runtime usage utilities
-4. B200-B599 are for bootstrapping
-5. The rest is for recipes.
+3. B5-B259 are for programs loaded at runtime.
+4. B260-B599 are for bootstrapping a new core.
+5. B600-B650 are for recipes.
 
-Blocks are currently not organized neatly. I'm planning the
-extraction of recipes into some kind of block "overlays" that
-would live in the recipes subfolder so each recipe would build
-its own specific blkfs which would contain only its recipe code,
-starting at B600.
+Recipes blocks do not live in the main blkfs, but each recipe
+has its own blkfs overlay, with blocks beginning at 600.

recipes/pcat/blk/612

@@ -3,7 +3,7 @@
 RS_ADDR 0x80 - CONSTANT SYSVARS
 30 LOAD   ( 8086 asm )
 262 LOAD  ( xcomp ) 270 LOAD  ( xcomp overrides )
-805 820 LOADR ( 8086 boot code )
+445 460 LOADR ( 8086 boot code )
 353 LOAD  ( xcomp core low )
 604 LOAD  ( KEY/EMIT drivers )
 606 608 LOADR  ( BLK drivers )