[Cin] fileexr/fileppm direct copy support

[Andrea paz]

Thanks Phyllis; I finally saw some difference:

AppImage (no patch)

render exr to exr:                   176 sec, 19.491 fps
render exr +plugin to exr:      183 sec, 18.717 fps


Build (patch)

render exr to exr:                   172 sec, 19.970 fps
render exr +plugin to exr:      173 sec, 19.8 fps