Fix overescaping in Paste

Summary:
Two issues:

  - When we read the content out of cache, it has lost its "safe html" flag, since the cache is raw-string oriented. Restore it.
  - explode() isn't safe-html-safe. Use phutil_split_lines() instead, which is.

Test Plan: Looked at /paste/

Reviewers: codeblock, chad

Reviewed By: codeblock

CC: aran

Differential Revision: https://secure.phabricator.com/D4980

src/applications/paste/controller/PhabricatorPasteController.php

@@ -44,7 +44,7 @@ abstract class PhabricatorPasteController extends PhabricatorController {
     PhabricatorPaste $paste,
     $max_lines = null) {
 
-    $lines = explode("\n", rtrim($paste->getContent()));
+    $lines = phutil_split_lines($paste->getContent());
 
     return id(new PhabricatorSourceCodeView())
       ->setLimit($max_lines)