Blender Git Loki

Fix crash drawing hair with older GPUs.

Some GPU's have support for compute shaders, but don't support
GLSL 4.3. This resulted in compiler errors and crashes.

This issue could have been solved by supporting older GLSL languages but
that would have been a hassle to get it right. We already have a
fallback in place for GPU's that don't support compute shaders at all.