Merge a small amount of remaining "libphutil/" code with Phabricator, break libphutil dependency

Summary: Ref T13395. Moves a small amount of remaining "libphutil/" code into "phabricator/" and stops us from loading "libphutil/".

Test Plan: Browsed around; there are likely remaining issues.

Maniphest Tasks: T13395

Differential Revision: https://secure.phabricator.com/D20981

scripts/init/lib.php

@@ -8,10 +8,14 @@ function init_phabricator_script(array $options) {
   ini_set(
     'include_path',
     $include_path.PATH_SEPARATOR.dirname(__FILE__).'/../../../');
-  @include_once 'libphutil/scripts/__init_script__.php';
-  if (!@constant('__LIBPHUTIL__')) {
-    echo "ERROR: Unable to load libphutil. Update your PHP 'include_path' to ".
-      "include the parent directory of libphutil/.\n";
+
+  $ok = @include_once 'arcanist/scripts/init/init-script.php';
+  if (!$ok) {
+    echo
+      'FATAL ERROR: Unable to load the "Arcanist" library. '.
+      'Put "arcanist/" next to "phabricator/" on disk.';
+    echo "\n";
+
     exit(1);
   }