Log Message:
Update shells/lshell to 0.15.1.
Security fix.

=== v0.9.15.1 15/03/2012 ===
    * Corrected security bug allowing user to get out of the restricted
    shell. Thank you bui from NBS System for reporting this grave issue!

=== v0.9.15 13/03/2012 ===
    * Set the hostname to the "short hostname" in the prompt.
    * Corrected traceback when "sudo" command was entered alone. Thank you
      Kiran Reddy for reporting this.
    * Added support for python2.3 as subprocess is not included by default.
    * Corrected the 'strict' behavior when entering a forbidden path.
    * Added short path promp support using the 'prompt_short' variable.
    * Corrected stacktrace when group did not exist.
    * Add support for empty prompt.
    * Fixed bugs when using $() and ``.
    * Corrected strict behavior to apply to forbidden path.
    * Added support for wildcard '*' when using 'cd'.
    * Added support for "cd -" to return to previous directory.
    * Updated security issue with non printable characters permitting user
      to get out of the limited shell.
    * Now lshell automatically reload its configuration if the configuration
      file is modified.
    * Added possibility to have no "intro" when user logs in. (by setting
      the intro configuration field to "")
    * Corrected multiple commands over ssh, and aliases interpretation.
    * Added possibility to use wildcards in path definitions.
    * Finally corrected the alias replacement loop.