Changing the call setup and return to be more efficient

Now we are using a statically linked list of messages. This will not work with procs, but that can be solved then.

Previous (wrong) thinking was that because of procs messages have to be allocated for every call. This was too slow, and not neccessary

lib/risc/register_value.rb

@@ -171,14 +171,6 @@ module Risc
       op
     end
 
-    # generate a Function return instruction
-    # using the register as the parameter where the return address is passed
-    def function_return
-      ret = Risc.function_return("return", self)
-      builder.add_code(ret) if builder
-      ret
-    end
-
     # create operator instruction for self and add
     # doesn't read quite as smoothly as one would like, but better than the compiler version
     def op( operator , right)