Update PHP 7.1 from 7.1.19 to 7.1.20

Changelog: http://www.php.net/ChangeLog-7.php#7.1.20

Also patch out MySQL 8 auth changes, which makes the hash
extension mandatory instead of optional and introduce further
bugs:
https://github.com/php/php-src/commit/d6e81f0bfd0cb90586dd83d4fd47a4302605261a

MFH: 2018Q3