[llvm] [SPIRV] Add support for pointers to functions with aggregate args/returns as global variables / constant initialisers (PR #169595)

[Juan Manuel Martinez Caamaño via llvm-commits]

https://github.com/jmmartinez commented:

Just a first go at it. I have spotted only 1 issue, the rest are cosmetic.

https://github.com/llvm/llvm-project/pull/169595