HTTPS fix

Some web server returns a $_SERVER['HTTPS'] = 'no value' for non https connections

ie. nginx-1.7.0 with php5-fpm, causing all navigation links to link to https when on http version of site

https://stackoverflow.com/questions/1175096/how-to-find-out-if-you-are-using-https-without-serverhttps
and why not ($_SERVER['HTTPS'] != 'off' || $_SERVER['HTTPS'] != '') ?