This commit adds a SPIR-V assembler header file.
swscale gets runtime-defined assembly once again!
The swscale internals currently have a quirk which causes the memcpy backend to be called when the pixfmts match.
It requires special handling.
libvidstab's vsTransformPrepare() takes different internal code paths for in-place (src == dest) vs.
The function macro emits AARCH64_VALID_CALL_TARGET for exported symbols, marking them as valid destinations for indirect _calls_.
Using AMF interfaces in C can be cumbersome and visually difficult to process in some cases: i.e.: object->function(object, args).