Adding a JSDoc configuration for generating metadata on exported symbols

This generates info for all symbols annotated with "@todo api" (when Plovr is replaced, this will become "@api").  Generated metadata is written to stdout.  A separate process will handle the output.

buildcfg/jsdoc/symbols/todo-plugin.js

@@ -0,0 +1,26 @@
+/**
+ * @fileoverview  This plugin should go away when we get rid of Plovr and can
+ * use Closure Compiler's extra_annotation_name option.  Until then, we hijack
+ * the todo tag to add doclet properties for other tags we eventually want to
+ * support.  For example, the "todo api" tag can eventually be replaced with
+ * the "api" tag.
+ */
+
+
+/**
+ * Our hook to define new tags.
+ * @param {Object} dictionary The tag dictionary.
+ */
+exports.defineTags = function(dictionary) {
+
+  dictionary.defineTag('todo', {
+    mustHaveValue: true,
+    onTagged: function(doclet, tag) {
+      var parts = tag.text.split(' ');
+      if (parts[0] === 'api') {
+        doclet.api = parts.slice(1).join(' ').trim();
+      }
+    }
+  });
+
+};