Support PHP error control operators

[twose]

Swoole\Runtime::enableCoroutine();
Swoole\Coroutine\run(function () {
    for ($n = 256; $n--;) {
        Swoole\Coroutine::create(function () {
            $context = stream_context_create(['http' => ['timeout' => 1]]);
            @file_get_contents('http://127.0.0.1:65535', false, $context);
        });
    }
});

EXPECT: no warning