~~This applies on top of !656, the last three commits belong here.~~
-- v12: vkd3d-shader/ir: Sort each loop by block label. vkd3d-shader/ir: Dump the loops in the control flow graph. vkd3d-shader/ir: Keep track of loops by header block. vkd3d-shader/ir: Keep a reference to the message context inside struct vsir_cfg.