[Issue 19160] wrong C++ mangle for const template args

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19160

--- Comment #3 from Nicholas Wilson <iamthewilsonator at hotmail.com> ---
https://github.com/dlang/dmd/pull/8432 is not part of 2.081.1 or 2.081.2. It is
however part of 2.082.beta-1.

Try with DMD 2.082.beta-1 or newer, confirm if it works. If so we can cherry
pick this onto LDC. If not I've got more fixing to do!

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