Blender Git Loki

Cycles: Better feedback about experimental features being used

Instead of having a label which basically duplicated the information
about experimental feature set being used (which had a bug because
it claimed experimental GPU kernel is used even if compute device is
CPU btw) now we've got an enum item icon.

So once you switched to experimental feature set you'll see an
exclamation mark icon in the enum, so you know something might be
unstable or slow.