this function was removed in PHP 5.4.0

The class loader isn't available at that place in inc/init.php so the
check if the sitemap is compressed didn't work.

Compressing a gzip file again for transport is standards compliant, but
some clients assume that the file is only compressed once then and don't
remove the outer compression layer. This could disable compression in
too many cases theses cases should be rare and shouldn't cause any
problems.

* noreply:
  renamed mailfromnon to mailfromnobody, use in subscriptions
  added mailfromnone internal option FS#2170

Conflicts:
	inc/subscription.php

* make use of $INPUT
* clean up coding style
* add phpdoc comments

makes it easier to access our do parameters

This fixes problems with setgid bits on the media directory