Fix {Fnnn} rule in Remarkup

Summary:
Remarkup rule callbacks now get SafeHTML matches instead of string matches. If they call:

  $some_lisk_dao->load($matches[1]);

..as is the case with the `{F123}` rule, we reject the SafeHTML as an invalid ID and return null.

Allow load() to string convert any object (which will either succeed or fatal in an obviously-broken way).

(Long ago we threw instead of returning null here, but it meant we had to do a lot of redundant checks.)

Test Plan: `{F123}` shows an image again. `{C1}` embeds a countdown.

Reviewers: vrana, chad

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D4961

src/infrastructure/markup/PhabricatorMarkupEngine.php

@@ -41,7 +41,7 @@ final class PhabricatorMarkupEngine {
 
   private $objects = array();
   private $viewer;
-  private $version = 3;
+  private $version = 4;
 
 
 /* -(  Markup Pipeline  )---------------------------------------------------- */

src/infrastructure/storage/lisk/LiskDAO.php

@@ -406,6 +406,10 @@ abstract class LiskDAO {
    * @task   load
    */
   public function load($id) {
+    if (is_object($id)) {
+      $id = (string)$id;
+    }
+
     if (!$id || (!is_int($id) && !ctype_digit($id))) {
       return null;
     }