This is analogous to the existing support for fixing up shader inputs.
It is intended to be used with tessellation to add implicit builtins
that are read from a later stage, despite not being written in an
earlier stage. (Believe it or not, this is in fact legal in Vulkan.)

Helps fix 8 CTS tests under `dEQP-VK.pipeline.*.no_position`. (Eight
other tests work solely by accident without this change.)

MSL: Add a mechanism to fix up shader outputs.

Approved-by: Steven Winston

It is possible in SPIR-V to declare multiple specialization constants
with the same constant ID. The most common cause of this in GLSL is
defining a spec constant, then declaring the workgroup size to use that
spec constant by its ID. But, MSL forbids defining multiple function
constants with the same function constant ID. So, we must only emit one
definition of the actual function constant (with the
`[[function_constant(id)]]` attribute); but we can point the other
variables at this one definition.

Fixes three tests in the Vulkan CTS under
`dEQP-VK.compute.basic.max_local_size_*`.

MSL: Deduplicate function constants.

Approved-by: Steven Winston

Does analysis of outputs and sorts them into buffers. Nothing else yet.

# Conflicts:
#	main.cpp
#	spirv_cross_c.cpp
#	spirv_cross_c.h
#	spirv_msl.cpp
#	spirv_msl.hpp

This only does the bare minimum needed to write XFB data (and not even
that actually). It still needs to calculate the offset in the buffer
where the data need to be written, and primitive types other than points
need to be implemented.

# Conflicts:
#	reference/shaders-msl/comp/local-size-duplicate-spec-id.comp
#	spirv_msl.cpp

…e updated to be used.

…ernels.

…sform feedback.

This lets us reference it later.

I don't expect this to build, let alone work. (Really, all these changes
ought to be squashed when merged to SPIRV-Cross.)

Work out how indexing works for triangle fans. A little bit closer...

It should be based on the number of primitives written.

Add missing instance term to the triangle fan base index.

We need to use a local copy because the vertex may need to be written
more than once.

Instead, go through the local variables we declared earlier.

Almost done.

This gives them the correct layout in memory.

That way, any nested structs get repacked as well.

This is the only type of shader that can even have such outputs. Not
only does this save some work in most cases, it also fixes a problem
with the next patch.

We still rely on it to pass around and collect the output. To avoid
duplicates, only do this if we would not do this normally.

Use the offset from the `XfbOutput` struct instead of querying it again
from the ID.

Use the `member_index` local instead of using `size() - 1` when setting
member decorations.

Don't set the qualified name for builtin block variabless--we handle
those a different way.

Use the member index from the `XfbOutput` when inspecing the original
block type instead of the `member_index` local. This one was a real bug;
honestly, I don't know how it even worked before.

…types.

Make sure they use the `thread` AS and that they have the `packed_`
prefix, if necessary.

Add missing changes from previous patch.

...on the builder and not for me.

…hash<enum> is supposed to just work.

…ordered_map.

…et also doesn't support enum in C++11 for hash key

Only gets the base of the primitive so far.