- fix build with libraw 0.20 (libraw_0_20.patch)

Try again, as last submit somehow didn't include last change, what the f**k?

I copied the fix from gentoo. I tried to verify if that is fine, but libraw neither documents this change in changelog nor is the history conclusive. Change comes in one big "Merge development branch to master" without any reference to the individual commits.

freeimage development seems dead and maybe should be replaced if possible.