This commit adds support for copying nested hierarchical types of split
types. E.g, a struct of a struct containing both user and builtin interstage
IO variables.
When copying split types, if any subtree does NOT contain builtin interstage
IO, we can copy the whole subtree with one assignment, which saves a bunch
of AST verbosity for memberwise copies of that subtree.
Rationalizes the entire tracking of the linker object nodes, effecting
GLSL, HLSL, and SPIR-V, to allow tracked objects to be fully edited before
their type snapshot for linker objects.
Should only effect things when the rest of the AST contained no reference to
the symbol, because normal AST nodes were not stale. Also will only effect such
objects when their types were edited.
Takes some pressure off of issue #304.
Structures don't inherit locations and then explicitly decorate
members with them, so removed this reason to have another instance
of a structure type.