debug: Add stub for instruction decoding

debug/chario.asm

@@ -28,7 +28,20 @@ crlf:	mov al, 0x0A
 	mov al, 0x0D
 	jmp putc
 
-print16:
+print_dl:
+	mov cl, 4
+	; repeat 2 times
+	call .c
+.c:	mov al, dl
+	shl dx, cl
+	shr al, cl
+	add al, 0x30
+	cmp al, 0x3a
+	jl putc
+	add al, 7
+	jmp putc
+
+print_dx:
 	mov cl, 4
 	; this double-call is essentially a 4 times repeating loop
 	call .c1
@@ -48,6 +61,19 @@ print16:
 	add al, 7
 	jmp putc
 
+print_esbx:
+	push cx
+	push dx
+	mov dx, es
+	call print_dx
+	mov al, ':'
+	call putc
+	mov dx, bx
+	call print_dx
+	pop dx
+	pop cx
+	ret
+
 	; Read character
 getc:	xor ax, ax
 	int 0x16