Description:
------------
With the introduction of typed class properties, there is also the nullable flag represented as a question mark, for example:

    class Foo
    {
        public ?string $bar;
    }

In keeping with the naming convention in ReflectionParameter and ReflectionType, the request is to also include a method with this name in the ReflectionProperty.

Test script:
---------------
class Foo
{
    public ?string $bar;
    public string $baz;
}

$barMeta = new ReflectionProperty(Foo::class, 'bar');
$bazMeta = new ReflectionProperty(Foo::class, 'baz');

var_dump( $barMeta->allowsNull() );
var_dump( $bazMeta->allowsNull() );


Expected result:
----------------
true
false