[Issue 18885] New: statfs struct was changed in FreeBSD 12

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18885

          Issue ID: 18885
           Summary: statfs struct was changed in FreeBSD 12
           Product: D
           Version: D2
          Hardware: x86_64
                OS: FreeBSD
            Status: NEW
          Severity: major
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: freeslave93 at gmail.com

core.sys.posix.sys.statvfs still has the declaration for FreeBSD 11.
That leads to segfeault when calling statfs function because of structure's
size mismatch.

Should we just update statfs_t declaration for FreeBSD (and drop support for
FreeBSD 11) or dispatch somehow?

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