[Issue 18461] core.bitop.bt returns garbage in release code

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18461

--- Comment #1 from feklushkin.denis at gmail.com ---
It is important to clarify: please run example several times, 10-20 times or so
and you will see difference in exit code values.

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