Drupal: load civicrm.css using drupal_add_css()

In the civicrm.module, I have changed the following in civicrm_html_head():

• $head = "<style type=\"text/css\">@import url({$config->resourceBase}css/civicrm.css);</style>\n";
  + drupal_add_css(drupal_get_path('module', 'civicrm') . '/../css/civicrm.css');

Since civicrm.css is always loaded anyway, it provides better performance if the css is loaded through Drupal so that it can be aggregated.