[Bug c/116130] Implement C23 N2956 paper - [[unsequenced]] and [[reproducible]] function type arguments

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116130

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
BTW, the rule about composite types sounds fairly dangerous in the ?: operator
case.
For redeclarations it is the right thing, but for ?: yielding the union of the
standard attributes will cause problems say on:
int foo (int);
[[unsequenced]] int bar (int);

int
baz (int x, int y)
{
  int a = (y ? &foo : &bar) (x);
  int b = (y ? &foo : &bar) (x);
  return a + b;
}