move all position setting into position

Position and subclasses handle the logic, external to
the classes, so it can be swapped out later
(at runtime positions can’t change)

test/arm/test_logic.rb

@@ -82,22 +82,22 @@ module Arm
     end
     def test_too_big_add
       code = @machine.add	 :r1 , :r1, 0x222
-      code.set_position(0,0)
+      Risc::Position.set(0,0)
       # add 0x02 (first instruction) and then 0x220 shifted
       assert_code code , :add , [0x02,0x1c,0x91,0xe2] #e2 91 1e 02
       # added extra instruction to add "extra"
       assert_code code.next , :add , [0x22,0x10,0x91,0xe2] #e2 91 10 22
     end
 
-    def label pos = 0x22 + 8
+    def label( pos = 0x22 + 8)
       l  = Risc.label("some" , "Label")
-      l.set_position   pos
+      Risc::Position.set(l,pos , 1)
       l
     end
 
     def test_move_object
       code = @machine.add( :r1 , label)
-      code.set_position(0,0)
+      Risc::Position.set(code,0,0)
       assert_code code , :add , [0x22,0x10,0x9f,0xe2] #e2 9f 10 22
     end