Fix declaring property named get/set/async

[kvinwang]

    class P {
        get;
        get = () => "123";
    }

Got SyntaxError: invalid property name.
This PR fixes it.

[saghul]

Is this a port from bellard/quickjs ?

[kvinwang]

Is this a port from bellard/quickjs ?

No, should I move this PR the the upstream? I submit it here because I use this fork in my project.
Looks like both repo are actively maintained. A bit confusing.

[saghul]

No need, I think this was fixed there too, that's why I asked.

[richarddd]

This fixes another pattern where we declare a property (without initalizing it) called get, and later initilizes is. My original QuickJS PR didn't consider this. Should be added to upstream as well.