[Issue 17821] atomicStore is buggy when target is larger than source

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=17821

--- Comment #2 from johanengelen at weka.io ---
Fixed in LDC 1.4.0.

The remaining issue is compilation error with DMD for:
```
import core.atomic;
shared ulong x;
atomicStore(x, 0);
```

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