https://issues.dlang.org/show_bug.cgi?id=22453

          Issue ID: 22453
           Summary: OpenBSD: Add a dummy value for AI_V4MAPPED
           Product: D
           Version: D2
          Hardware: All
                OS: Other
            Status: NEW
          Severity: minor
          Priority: P1
         Component: druntime
          Assignee: nobody@puremagic.com
          Reporter: bcallah@openbsd.org

OpenBSD doesn't support AI_V4MAPPED but real-world D code assumes its presence.
Add a dummy value of 0 to help prevent compiler errors (but, of course, without
the benefits of AI_V4MAPPED).
Discovered when building some code from the dub packages.

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