shader: Work around out-of-bounds buffer and image access
Make TGSI accept a negative image index, and handle it in the shader conversion code.
This should stabilize spec@arb_shader_image_load_store@execution@image-array-out-of-bounds-access-load
Make TGSI accept a negative image index, and handle it in the shader conversion code.
This should stabilize spec@arb_shader_image_load_store@execution@image-array-out-of-bounds-access-load