[Issue 20174] New: 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

          Issue ID: 20174
           Summary: posix-only std.math functions shouldn't be present on
                    windows
           Product: D
           Version: D2
          Hardware: All
                OS: Windows
            Status: NEW
          Severity: normal
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: john.loughran.colvin at gmail.com

they should be completely versioned out, otherwise you end up confusingly
crashing at runtime (with "Illegal Instruction"!!!).

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