[Issue 23697] ImportC: No examples of invalid forward references in C code accepted by ImportC

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23697

--- Comment #4 from Iain Buclaw <ibuclaw at gdcproject.org> ---
Another example of forward reference code that is accepted by ImportC, rejected
by standard C.

```
struct S s;
int* p = &s.t.x;
struct S { int a; struct T t; };
```

Giving both as examples on the ImportC documentation page would be good enough.

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