[Issue 21976] importC: enumeration constants rejects conditional expressions in parentheses

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21976

--- Comment #1 from Iain Buclaw <ibuclaw at gdcproject.org> ---
Likewise, this fails to compile:
---
enum constant_expression
{
  ce_first,
  ce_second = (int) ((1UL << (ce_first)) << 24),
};

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