nop
rot (abc-bca)
-rot (abc-cab)
dup (x-xx)
swap (xy-yx)
over (xy-xyx)
drop (xy-x)
tuck (xy-yxy)
nip (xy-y)
lit (-l)
equal (xy-f)
nequal (xy-f)
add (xy-z)
sub (xy-z)
mul
div
neg
slt
ult
sle
ule
lod (a-d)
sto (da-)
push
pop

want:
calls (15 bits)
j, cj, relative addr, 8 bits
lit, 4 or 8 or 16 bits
mark,loc,ret, + 4bit arg
regular op, no arg (between 16 and 32 of these)

CALL (addr:15)
or
JMP (cond?:1) (rdst:rest)
or 
(mark/loc/ret/lit4) (arg:4)
or

regular op (7 bits)



OPW:7: 1 T:2 arg:4
OPR:7: 0 opcode:6
that is,
	00 - 3f regular opcodes	(64 of them)
	4x	mark x
	5x	loc x
	6x	ret x
	7x	lit4 x

I: 0 0 (OPW|OPR) (OPW|OPR)
J: 0 1 0 cond? raddr:12
L: 0 1 1 value:13
C: 1 addr:15