Added new section for PDF documentation

git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@172128 13f79535-47bb-0310-9956-ffa450edef68

doc/xerces-c_book.xml

@@ -37,6 +37,8 @@
   <document id="caveats"     label="Caveats"      source="caveats.xml"    />
   <document id="feedback"    label="Feedback"     source="feedback.xml"   />
 
+  <separator/>
+  <document id="pdf"    label="PDF Document"     source="pdf-c.xml"   />
   <separator/>
   <external href="http://&XercesDistDir;/"     label="Download"    />
   <external href="http://xml.apache.org/from-cvs/xml-xerces/"     label="Dev Snapshots"    />