Get rid of stability annotations and document stability with api

This change adds a stability value to the api annotation, with
'experimental' as default value.

enum, typedef and event annotations are never exportable, but
api annotations are needed there to make them appear in the
docs.

Nested typedefs are no longer inlined recursively, because the
resulting tables get too wide with the current template.

apidoc/plugins/api.js

@@ -1,3 +1,29 @@
+/**
+ * Define an @api tag
+ */
+var conf = env.conf.stability;
+var defaultLevels = ["deprecated","experimental","unstable","stable","frozen","locked"];
+var levels = conf.levels || defaultLevels;
+var util = require('util');
+exports.defineTags = function(dictionary) {
+  dictionary.defineTag('api', {
+    mustHaveValue: false,
+    canHaveType: false,
+    canHaveName: false,
+    onTagged: function(doclet, tag) {
+      var level = tag.text || "experimental";
+      if (levels.indexOf(level) >= 0) {
+        doclet.stability = level;
+      } else {
+        var errorText = util.format('Invalid stability level (%s) in %s line %s', tag.text, doclet.meta.filename, doclet.meta.lineno);
+        require('jsdoc/util/error').handle( new Error(errorText) );
+      }
+    }
+  });
+};
+
+
+
 /*
  * Based on @stability annotations, and assuming that items with no @stability
  * annotation should not be documented, this plugin removes undocumented symbols