Accept empty aggregate initializers when emulating clang versions before 17 []

[jketema]

I'm not able to open an issue, as that is currently restricted to contributors, of which I am not one. Hence, I'm just opening a PR with a fix, which I understand is not ideal.

We noticed a regression where empty initializers for aggregates are no longer accepted when emulating clang versions before clang 17. For example, the following fails with EDG 7.0:

  struct A {
    int i;
  };

  struct A a = {};

This seems to be due to the changes made as part of EDGcpfe/29042. This PR restores the behavior for empty aggregate initializers. Note that I picked clang 2.9 as the lower bound, as that was the minimum version I was reasonably able to test against.

[daveedvdv-nvidia]

Was Clang 2.9 really the first version which enabled this?
Otherwise, it might be clearer to just go with clangc_version_is(any_version)?

[jketema]

Note that I picked clang 2.9 as the lower bound, as that was the minimum version I was reasonably able to test against.

As a wrote "Note that I picked clang 2.9 as the lower bound, as that was the minimum version I was reasonably able to test against.", but let me do some further digging and get back to you.

[daveedvdv-nvidia]

Ah yes, sorry, I missed that.
Thanks for investigating... generally-speaking, I think it's acceptable to emulate for clangc_version_is(any_version) if it can be reproduced as far back as Clang 3.8.

Also, I've open issue #238 for this (to use [GH #238] as the Changes entry tag).