Tweak the javadoc task to make it use a 1.4 JDK. Uses the same javahome.jdk14 property as for Forrest.

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/branches/fop-0_94@567303 13f79535-47bb-0310-9956-ffa450edef68

build.xml

@@ -1008,6 +1008,7 @@ NOTE:
     <mkdir dir="${build.javadocs.dir}"/>
 
     <javadoc
+      executable="${javahome.jdk14}/bin/javadoc"
         packagenames="${javadoc.packages}"
         destdir="${build.javadocs.dir}"
         author="true"