This adds a pure PHP implementation of the cryptographic functions supported in PHP 7.2+. It provides the necessary backwards compatibility required to support signature verification and other security features going forward across all supported PHP versions.
Props paragoninitiativeenterprises
Fixes#45806. See #39309.
Built from https://develop.svn.wordpress.org/trunk@44953
git-svn-id: http://core.svn.wordpress.org/trunk@44784 1a063a9b-81f0-0310-95a4-ce76da25c4cd
