This avoids a lot of huge code changes.
Arrays generally cannot be copied in and out of buffers, at least no
compiler frontend seems to do it.
Also avoids a lot of issues surrounding packed vectors and matrices.
MSL generally emits the aliases, which means we cannot always place the
master type first, unlike GLSL and HLSL. The logic fix is just to
reorder after we have tagged types with packing information, rather than
doing it in the parser fixup.
