[Issue 19740] Incorrect result of BigInt * BigInt

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19740

--- Comment #5 from shove <shove at 163.com> ---
Reposition request resubmitted:

https://github.com/dlang/phobos/pull/6967

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