Hi Davey,
It seems PHP 7.1's UPGRADING is miss merged in last few days.
https://github.com/php/php-src/blob/PHP-7.1/UPGRADING
This seems the last valid UPGRADING for 7.1.
http://git.php.net/?p=php-src.git;a=blob;f=UPGRADING;hb=28edc971e74e7426b496945fe62628ea582f0a72
Regards,
