Gracefully handle template literal properties in the parser

var x = {
    a: "Hello"
    `b`: 123
}

Right now, the parser encounters the template string, decides it should bail out of object literal parsing, and we more or less recover thinking we have something like the following:

var x = ({ a: "Hello" } `b`) : 123 }

So we'll report an error on what we think is:

{ a: "Hello" } `b`

• On the syntactic layer under ES5 mode, we'll say tagged templates are not supported unless in ES6.
• On the semantic layer, we'll say { a: "Hello" } is not invokable.

从 parser 的对象字面量处理开始，在 ES5 和 ES6 模式下重现所示的模板字面量属性案例。跟踪 parser 如何在模板字符串处进行恢复，并比较由此产生的语法诊断和语义诊断。完成的标准是：这个格式错误或不受支持的构造能够获得适当的诊断，而不会被误读为带标签调用。