Fix #34672: Image sampling line didn't use color management for byte buffers

This makes it so sample line (for all image editor, sequencer and compositor)
displaying managed color for byte buffers as well. It was simply not implemented
before.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55367 954f8c5b-7b00-dc11-b283-0030488c597c