merge 5.1 => 5.5

sql/filesort.cc

-/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -281,9 +281,7 @@ ha_rows filesort(THD *thd, TABLE *table, SORT_FIELD *sortorder, uint s_length,
       Use also the space previously used by string pointers in sort_buffer
       for temporary key storage.
     */
-    param.keys=((param.keys *
-                 (param.rec_length+sizeof(char*))) /
-		param.rec_length - 1);
+    param.keys= table_sort.sort_keys_size / param.rec_length;
     maxbuffer--;				// Offset from 0
     if (merge_many_buff(&param,(uchar*) sort_keys,buffpek,&maxbuffer,
 			&tempfile))