Rolling this out of T13871, which was asking for _support_ for JPEG 2000 images. Since they're not widely supported by browsers and they're a lossy format without a clear benefit to use I'm WONTFIXing that for now, but the upload bug that makes it possible to mistakenly upload them remains.
is an example of a file that was first uploaded as JPEG 2000 (the current version was correctly converted to regular JPEG).
is an example mentioned also on the previous bug which I reuploaded to test to confirm the bug is still present.
File file type is being detected as image/jp2, but this shouldn't make it past upload since it shouldn't match '.jpg' file extension...