v3: Emit a FIXME if we see multiple RDEF sections. Use require_space() in get_section_data() and change the arguments to separate count and size. Pass a vkd3d_shader_code struct to get_section_data() and rename it to get_data_ptr().
Also, add the tests and necessary HLSL compiler fixes. This makes the series rather large, but we're in code freeze anyway, so hopefully that's fine to review anyway.