Blender Git Loki

Render: Extend the passtype field of RenderPasses to 64 bit

This commit extends the number of possible pass types to 64 bit. However, it only
affects the structures used for storage during and after rendering, not the SceneRenderLayer
that's visible to the user (due to various limitations to 32 bit integers in RNA).
Therefore, their main purpose is to be allocated by the renderer based on some other setting.