MFH: r487427

Update to 8.7.21

Changelog: https://typo3.org/article/typo3-952-8721-and-7632-security-releases-published/

PR: 233935
Security: bab29816-ff93-11e8-b05b-00e04c1ea73d
Sponsored by: Netzkommune GmbH

Approved by: ports-secteam (miwi)