Functions are not first class objects in GLSL, so there is never a value
of function type. No code actually used this except for one function
which asserted it shouldn't occur. One comment mentioned it, but was
incorrect. So we may as well remove it entirely.
As of 1.20, variable names, function names, and structure type names all
share a single namespace, and should conflict with one another in the
same scope, or hide each other in nested scopes.
However, in 1.10, variables and functions can share the same name in the
same scope. Structure types, however, conflict with/hide both.
Fixes piglit tests redeclaration-06.vert, redeclaration-11.vert,
redeclaration-19.vert, and struct-05.vert.
Since the types are singletons across the lifetime of the compiler,
repeatedly compiling a program with the same structure type defined
would drop a copy of the array on the floor per compile.
This is a bit tricky because the static GLSL types are not called with
the talloc-based new, so we have to use the global type context, which
may not be initialized yet.
All scalar, vector, and matrix constructors are generated in-line
during AST-to-HIR translation. There is no longer any need to
generate function versions of the constructors.