Add <compatibility> notes for changes made in version 2.4.2 + fix a typo not...

Add <compatibility> notes for changes made in version 2.4.2 + fix a typo not backported in 2.4 branch

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1585830 13f79535-47bb-0310-9956-ffa450edef68