rewrite handle_if_return

optimizations of if/return/continue seem to be even better now

lib/output.js

@@ -892,6 +892,7 @@ function OutputStream(options) {
     DEFPRINT(AST_Undefined, function(self, output){
         // XXX: should add more options for this
         output.print("void 0");
+        //output.print("[][0]");
     });
     DEFPRINT(AST_This, function(self, output){
         output.print("this");