synch 2.4.x with trunk.

When r1729208 has been backported in 2.4.x (see r1743576), a coment has been missed in the backport proposal and has never reached 2.4.x.

Add it now, in order to synch a bit the 2 branches.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1855572 13f79535-47bb-0310-9956-ffa450edef68