Fix lossless image rotation

Apparently, the old code was based on libjpeg6. However, most systems use
libjpeg8 now, which has a few new features like cropping, leading to a lot
of fuckup with feh on libjpeg8 systems. Now feh works with libjpeg8,
but probably doesn't support libjpeg6 anymore.

Also, this code copypasta really sucks :-)