[Issue 20174] posix-only std.math functions shouldn't be present on windows

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20174

John Colvin <john.loughran.colvin at gmail.com> changed:

           What    |Removed                     |Added
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           Keywords|                            |accepts-invalid, industry,
                   |                            |trivial

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