Fix highlighting for stream typeahead in compose box.

Recently the typeahead for streams in the compose box was modified so
that streams only matched queries when the query was a prefix to the
stream.  When that change was made, the old highlighting behavior
had been mistakenly left in place.  This commit fixes the highlighting.

(imported from commit b7ec33daba46978df58eb91306686a4f1a57c7fa)

zephyr/static/js/composebox_typeahead.js

@@ -180,7 +180,10 @@ exports.initialize = function () {
             return subs.subscribed_streams();
         },
         items: 3,
-        highlighter: composebox_typeahead_highlighter,
+        highlighter: function (item) {
+            var query = this.query;
+            return typeahead_helper.highlight_query_in_phrase(query, item);
+        },
         matcher: function (item) {
             // The matcher for "stream" is strictly prefix-based,
             // because we want to avoid mixing up streams.