generalise the operator handling

ie passing them through
implementing more

lib/risc/boot.rb

@@ -181,7 +181,10 @@ module Risc
       end
 
       obj = space.get_class_by_name(:Integer)
-      [ :putint, :div4, :div10, :+ , :- , :*].each do |f|   #div4 is just a forward declaration
+      Risc.operators.each do |op|
+        obj.instance_type.add_method Builtin::Integer.operator_method(op)
+      end
+      [:putint, :div4, :div10].each do |f|   #div4 is just a forward declaration
         obj.instance_type.add_method Builtin::Integer.send(f , nil)
       end
     end