Merge r1737476 from trunk:

Add the <!--#comment ... --> syntax.
Idea from Rob.
Submitted by: jailletc36
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1747054 13f79535-47bb-0310-9956-ffa450edef68