[Issue 22598] importC: Add support for __extension__ keyword

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22598

Walter Bright <bugzilla at digitalmars.com> changed:

           What    |Removed                     |Added
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                 CC|                            |bugzilla at digitalmars.com

--- Comment #2 from Walter Bright <bugzilla at digitalmars.com> ---
The __extension__ documentation is confusing:

"You can prevent such warnings within one expression by
writing `__extension__' before the expression.  `__extension__' has no
effect aside from this."

Yet in your example,

   __extension__({ if (expr); else ...})

is a statement, not an expression.

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