Implement a basic hook_drush_command for help

I installed this module into ~/.drush as suggested in the Aegir handbook (instead of running drush dl provisionacl-6.x which doesn't work on Debian).

Wanting to verify the correct installation of the module, I tried in vain to run drush provisionacl and drush help provisionacl, each time resulting in an error message indicating that no "provisionacl" command was available.

By reading the code I figured out that the module simply has no command-line interface because it hooks directly into other drush commands (provision).

It might help to add a really simple hook so that simple-minded folks like me don't bang their heads over the installation of provisionacl. Could go something like this :

/**
 * Implementation of hook_drush_command().
 */
function provisionacl_drush_command() {
  $items['provisionacl'] = array(
    'description' => "Hooks into aegir-provision to setup ACL on client sites.\n\nNot intented to be used on the command line.",
  );

  return $items;
}