Fixes T6847. These symbols should always be classes, as interfaces cannot have methods defined.

<?php

Foo::bar();

> ./scripts/phutil_symbols.php test.php
{
  "have": [],
  "need": {
    "class": {
      "Foo": 7
    }
  },
  "xmap": []
}

(We should really have some test cases defined for this file)