use slot constants

lib/register/enter_implementation.rb

@@ -7,7 +7,7 @@ module Register
         # save return register and create a new frame
         to = RegisterReference.new(:r0)  # message base
         pc = RegisterReference.new(:pc)
-        move1 = RegisterMachine.instance.str( pc , to , Virtual::Message::RETURN )
+        move1 = RegisterMachine.instance.str( pc , to , Virtual::Slot::RETURN )
         block.replace(code , [move1] )
       end
     end

lib/register/return_implementation.rb

@@ -6,7 +6,7 @@ module Register
         #load the return address into pc, affecting return. (other cpus have commands for this, but not arm)
         message = RegisterReference.new(:r0)
         pc = RegisterReference.new(:pc)
-        move1 = RegisterMachine.instance.ldr( pc ,message , Virtual::Message::RETURN )
+        move1 = RegisterMachine.instance.ldr( pc ,message , Virtual::Slot::RETURN )
         block.replace(code , [move1] )
       end
     end

lib/virtual/message.rb

@@ -20,9 +20,6 @@ module Virtual
   # During compilation Message and frame objects are created to do type analysis
 
   class Message
-    RETURN = 2
-    EXCEPTION = 3
-    SELF = 4
 
     SELF_REG = :r0
     MESSAGE_REG = :r1