Blender Git Loki

Color management: get rid of original byte buffer partial update

It was only used by opengl render and in fact it needed just to
set DISPLAY_BUFFER_INVALID flag for the image buffer.

In theory it wouldn't make any change to opengl render speed
(because this change just moved rect_from_float from color
management code to image save code). And could not see any speed
changes on my laptop.