HLSL allows a range of types for clip and cull distances. There are
three dimensions, including arrayness, vectorness, and semantic ID.
SPIR-V requires clip and cull distance be a single array of floats in
all cases.
This code provides input side conversion between the SPIR-V form and
the HLSL form. (Output conversion was added in PR #947 and #997).
This PR extends HlslParseContext::assignClipCullDistance to cope with
the input side conversion. Not as much changed as appears: there was
also a lot of renaming to reflect the fact that the code now handles
either direction.
Currently, non-{frag,vert} stages are not handled, and are explicitly
rejected.
Fixes#1026.
