[Issue 19260] extern(C++) `T* const` mangling

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19260

--- Comment #9 from kinke at gmx.net ---
-1, as that won't work for `T *const *`, i.e., only for a very specific case,
so I find a dedicated UDA + compiler complexity a total overkill.

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