change to_risc and builtin code according to last commit

Wherever space was loaded to get to the next_message
we now load the Message factory.
Otherwise much the same, only the attribute is next_object, not next_message
The binary is growing with 1k objects per factory, so i had to fix (hack) arm to handle bigger constants
close #14

test/risc/test_interpreter.rb

@@ -54,7 +54,7 @@ module Risc
     end
     def test_pc1
       @interpreter.tick
-      assert_equal 49992 , @interpreter.pc
+      assert_equal 174632 , @interpreter.pc
     end
     def test_tick2
       @interpreter.tick
@@ -68,7 +68,7 @@ module Risc
     def test_pc2
       @interpreter.tick
       @interpreter.tick
-      assert_equal 49996 , @interpreter.pc
+      assert_equal 174636 , @interpreter.pc
     end
     def test_tick_14_jump
       14.times {@interpreter.tick}