Search callback for "add page" selector

Necessary since we now default $showSearch=true in TreeDropdownField.
See https://github.com/silverstripe/silverstripe-framework/pull/2364

code/controllers/CMSPageAddController.php

@@ -81,6 +81,16 @@ class CMSPageAddController extends CMSPageEditController {
 				)
 			)
 		);
+		$parentField->setSearchFunction(function ($sourceObject, $labelField, $search) {
+			return DataObject::get(
+				$sourceObject, 
+				sprintf(
+					"\"MenuTitle\" LIKE '%%%s%%' OR \"Title\" LIKE '%%%s%%'",
+					Convert::raw2sql($search),
+					Convert::raw2sql($search)
+				)
+			);
+		});
 
 		// TODO Re-enable search once it allows for HTML title display, 
 		// see http://open.silverstripe.org/ticket/7455