[TASK] Declare t3lib_treeView abstract

t3lib_treeView is the base class for trees and is always
extended by other classes for specific trees.
The patch adds the abstract keyword to the class declaration.

Change-Id: I5a54f1339ccf84c16671d0dd19bb4bc9d1f5747c
Resolves: #39816
Releases: 6.0
Reviewed-on: http://review.typo3.org/13695
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn

t3lib/class.t3lib_treeview.php

@@ -24,25 +24,19 @@
  *
  *  This copyright notice MUST APPEAR in all copies of the script!
  ***************************************************************/
-/**
- * Contains base class for creating a browsable array/page/folder tree in HTML
- *
- * Revised for TYPO3 3.6 November/2003 by Kasper Skårhøj
- *
- * @author Kasper Skårhøj <kasperYYYY@typo3.com>
- * @coauthor René Fritz <r.fritz@colorcube.de>
- */
 
 /**
  * Base class for creating a browsable array/page/folder tree in HTML
  *
  * @author Kasper Skårhøj <kasperYYYY@typo3.com>
- * @coauthor René Fritz <r.fritz@colorcube.de>
+ * @author René Fritz <r.fritz@colorcube.de>
  * @package TYPO3
  * @subpackage t3lib
- * @see t3lib_browsetree, t3lib_pagetree, t3lib_foldertree
+ * @see t3lib_browsetree
+ * @see t3lib_pagetree
+ * @see t3lib_foldertree
  */
-class t3lib_treeView {
+abstract class t3lib_treeView {
 
 		// EXTERNAL, static:
 		// If set, the first element in the tree is always expanded.