Prevent resolveReferences.js from pruning internal references we use

The script logic was returning early for all internal references
which were not also directly referenced by the main content (for
instance "class" and "text node" from Core AAM).

The script already keeps track of unused (by the main content) in
the termNames array. Therefore, we can check that array to see if
it contains the parent glossary term. If so, then return early like
before. Otherwise, let the script proceed.

Addresses github issue #20.

script/resolveReferences.js

@@ -197,7 +197,8 @@ function updateReferences(base) {
 }
 
 // We should be able to remove terms that are not actually
-// referenced from the common definitions
+// referenced from the common definitions. This array is
+// indexed with the element ids of the dfn tags to be pruned.
 var termNames = [] ;
 
 function restrictReferences(utils, content) {
@@ -224,7 +225,8 @@ function restrictReferences(utils, content) {
 // New logic: If the reference is within a 'dl' element of
 // class 'termlist', and if the target of that reference is
 // also within a 'dl' element of class 'termlist', then
-// consider it an internal reference and ignore it.
+// consider it an internal reference and ignore it -- assuming
+// it is not part of another included term.
 
 require(["core/pubsubhub"], function(respecEvents) {
     "use strict";
@@ -236,8 +238,14 @@ require(["core/pubsubhub"], function(respecEvents) {
                 var t = $item.attr('href');
                 if ( $item.closest('dl.termlist').length ) {
                     if ( $(t).closest('dl.termlist').length ) {
-                        // do nothing
-                        return;
+                        // Figure out the id of the glossary term which holds this
+                        // internal reference and see if it will be pruned (i.e.
+                        // is in the termNames array). If it is, we can ignore
+                        // this particular internal reference.
+                        var dfn = $item.closest('dd').prev().find('dfn');
+                        var parentTermId = dfn.makeID('dfn', dfn.getDfnTitles[0]);
+                        if (termNames[parentTermId])
+                            return;
                     }
                 }
                 var r = t.replace(/^#/,"") ;