Don't let DRUSH_SELECTED_URI be an array() due to odd empty array default in drush_get_context().
Remove call to _drush_bootstrap_select_drupal_site() during drush_bootstrap_validate().
Convince quick-drupal to pass its tests. Wish it used drush_invoke_process() to isolate steps better.
Delete a stray copy of drush_bootstrap_validate(). Must have meant to be on the class but lets just keep the copy in Drush/Boot/bootstrap.inc