Fix dtd to match <glossary> change in xsl.
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@290761
13f79535-47bb-0310-9956-
ffa450edef68
<!-- The glossary element defines a special case of link. The referenced
target is the name of an anchor within the glossary -->
<!ELEMENT glossary %Inline;>
-<!ATTLIST glossary ref CDATA #REQUIRED>
+<!ATTLIST glossary ref CDATA #IMPLIED>
<!-- The phonetic element should be used only within the glossary. It
describes a pronounciation -->