openbox: fix PR format and use new update-alternatives syntax

* fixes:
  NOTE: recipe openbox-3.5.0-1: task do_package: Started
  WARNING: openbox: Use of ALTERNATIVE_NAME is deprecated, see
  update-alternatives.bbclass for more info.
* bump PE if you care about upgrade path from wrong PR, introduced in
  commit 3becce85


  Author: Mario Domenech Goulart <mario@ossystems.com.br>
  Date:   Mon Dec 3 16:03:23 2012 +0000

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>