allow get_slot with two registers

before was register and number, but for runtime that doesn’t work

lib/interpreter/interpreter.rb

@@ -120,7 +120,12 @@ module Interpreter
 
     def execute_GetSlot
       object = object_for( @instruction.array )
-      value = object.internal_object_get( @instruction.index )
+      if( @instruction.index.is_a?(Numeric) )
+        index = @instruction.index
+      else
+        index = get_register(@instruction.index)
+      end
+      value = object.internal_object_get( index )
       #value = value.object_id unless value.is_a? Fixnum
       set_register( @instruction.register , value )
       true

lib/register/instructions/get_slot.rb

@@ -24,7 +24,7 @@ module Register
       @index = index
       @register = register
       raise "index 0 " if index == 0
-      raise "not integer #{index}" unless index.is_a? Numeric
+      raise "Not integer or reg #{index}" unless index.is_a?(Numeric) or RegisterValue.look_like_reg(index)
       raise "Not register #{register}" unless RegisterValue.look_like_reg(register)
       raise "Not register #{array}" unless RegisterValue.look_like_reg(array)
     end