change return sequence to return messages to space

as it was before blocks
(thought blocks would make reuse of messages impossible, but was wrong, this only appilies to lambdas)
(too) many tests affected

test/risc/test_interpreter.rb

@@ -54,7 +54,7 @@ module Risc
     end
     def test_pc1
       @interpreter.tick
-      assert_equal 25400 , @interpreter.pc
+      assert_equal 25656 , @interpreter.pc
     end
     def test_tick2
       @interpreter.tick
@@ -68,7 +68,7 @@ module Risc
     def test_pc2
       @interpreter.tick
       @interpreter.tick
-      assert_equal 25404 , @interpreter.pc
+      assert_equal 25660 , @interpreter.pc
     end
     def test_tick_14_jump
       14.times {@interpreter.tick}