Extended group context to Printer-Friendly group pages

Extended group context to "Printer-Friendly" group pages. This allows oglogo to work. In og_user_roles_all_roles():

// print.module (printer friendly)
//
// http://www.mysite.com/print/14
if (arg(0) == 'print' && is_numeric(arg(1))) {
$location = 201;
$nid = (int)arg(1);
$gid = og_user_roles_getgid($nid, $uid);
// Set group context.
$group_node = node_load($gid);
og_set_group_context($group_node);
}