add block_scope to --output ast

bin/uglifyjs

@@ -268,6 +268,13 @@ function run() {
                 var result = {
                     _class: "AST_" + value.TYPE
                 };
+                if (value.block_scope) {
+                    result.block_scope = {
+                        variables: value.block_scope.variables,
+                        functions: value.block_scope.functions,
+                        enclosed: value.block_scope.enclosed,
+                    };
+                }
                 value.CTOR.PROPS.forEach(function(prop) {
                     result[prop] = value[prop];
                 });