Use "originalsecret" value to obtain the URL of originals

I am not certain if the Flickr module already has support for original-size photos. As far as I can tell, every time I try to get the original of a photo using the Flickr module, it fails. I get the wrong URL and when trying to load the image, all I can see is an error image from Flickr saying the picture is currently unavailable.

I had to patch the flickr.inc file in order to allow the module to fetch the original size. When trying to obtain the URL of an original, it will use the "originalsecret" value rather than the usual "secret" value to generate the URL.

The patch is attached to this issue page for everyone's review.