Merge "Apply IP blocks to X-Forwarded-For header"

diff --cc RELEASE-NOTES-1.21
Simple merge

diff --cc includes/DefaultSettings.php
Simple merge

diff --cc includes/User.php
Simple merge

diff --cc languages/messages/MessagesEn.php
Simple merge

diff --cc languages/messages/MessagesQqq.php
Simple merge

diff --cc maintenance/language/messages.inc
Simple merge