Bug#25408 5.1 Can't compile on Windows

- DBUG_ENTER must be called before assignment on Windows and Netware.

storage/myisam/mi_packrec.c

@@ -592,8 +592,8 @@ static uint copy_decode_table(uint16 *to_pos, uint offset,
 			      uint16 *decode_table)
 {
   uint prev_offset;
-  prev_offset= offset;
   DBUG_ENTER("copy_decode_table");
+  prev_offset= offset;  
 
   /* Descent on the left side. */
   if (!(*decode_table & IS_CHAR))