[php-langspec][Issue #191] - Array Comparison

You can view the Issue on github:
https://github.com/php/php-langspec/issues/191

Opened By: Fleshgrinder
Issue Description:
In note 5. about array comparison the following is stated:

> If the next key in the left-hand operand does not exist in the right-hand operand, the arrays cannot be compared and `FALSE` is returned.

This is actually not true in case of the spaceship operator on both PHP and HHVM.

```php
<?php

$lhs = [0 => 0];
$rhs = [1 => 1];

var_dump(
    $lhs < $rhs,
    $lhs <= $rhs,
    $lhs <=> $rhs,
    $lhs >= $rhs,
    $lhs > $rhs
);

/*
bool(false)
bool(false)
int(1)
bool(false)
bool(false)
*/
```