Tie all the pieces for symbol cross-references together

Summary:
This makes symbol cross-references work in Differential. You need to do a little
legwork but I'll document that once the change has baked for a little while.

Basically:

  - Projects are annotated with indexed languages, and "shared library" projects
(for example, symbols in Phabricator should be searched for in Arcanist and
libphutil).
  - When we render a changeset, we check if its language is an indexed one. If
it is, we invoke the decorator Javascript.
  - The Javascript takes you to a lookup page, which either gives you a list of
matching symbols (if several match) or redirects you instantly to the
definition.

Test Plan: Clicked class and function symbols in a diff, got jumped into
sensible sorts of places in Diffusion.

Reviewers: jungejason, nh, tuomaspelkonen, aran

Reviewed By: jungejason

CC: aran, jungejason

Differential Revision: 980

webroot/rsrc/js/application/repository/repository-crossreference.js

@@ -22,7 +22,10 @@ JX.behavior('repository-crossreference', function(config) {
       if (JX.DOM.isNode(target, 'span') && (target.className in map)) {
         var uri = JX.$U('/diffusion/symbol/' + target.innerHTML + '/');
         uri.addQueryParams({
-          type : map[target.className]
+          type : map[target.className],
+          lang : config.lang,
+          projects : config.projects.join(','),
+          jump : true
         });
         window.open(uri);
         e.kill();