Link interfaces as classes

Summary:
We link classes from `extends` and `instanceof` (which can be both interface and class) and from `implements` (which is always interface).

We don't need to split these two because they share the same namespace.
If we decide to then we will need to:

- Fix [[ https://secure.phabricator.com/diffusion/P/browse/master/src/applications/diffusion/controller/DiffusionSymbolController.php;66a300768a62bbc9$79 | DiffusionSymbolController ]]
- Fix [[ https://secure.phabricator.com/diffusion/P/browse/master/webroot/rsrc/js/application/repository/repository-crossreference.js;66a300768a62bbc9$24 | repository-crossreference ]]
- Allow more types in `DiffusionSymbolController`.

Test Plan: Ran the script on secure.phabricator.com, clicked on `ArcanistLintRenderer` symbol.

Reviewers: epriestley, alanh

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3382

scripts/symbols/generate_php_symbols.php

@@ -63,7 +63,8 @@ foreach (Futures($futures)->limit(8) as $file => $future) {
   $interfaces = $root->selectDescendantsOfType('n_INTERFACE_DECLARATION');
   foreach ($interfaces as $interface) {
     $interface_name = $interface->getChildByIndex(1);
-    print_symbol($file, 'interface', $interface_name);
+    // We don't differentiate classes and interfaces in highlighters.
+    print_symbol($file, 'class', $interface_name);
     $scopes[] = array($interface, $interface_name);
   }