Blender Git Loki

Cycles: Gracefully handle out-of-memory happening in device vector

Currently only image loading benefits of this and will give magenta color
when image manager detects it's running out of memory.

This isn't ideal solution and can't handle all cases. For example, OOM
killer might kill process before it realized it run out of memory, but
in other cases this could prevent some crashes.

Reviewers: juicyfruit, dingto

Differential Revision: https://developer.blender.org/D1502