[MacPorts] #57109: cquery @20180718 shared_timed_mutex introduced in macOS 10.12

[MacPorts]

#57109: cquery @20180718 shared_timed_mutex introduced in macOS 10.12
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  Reporter:  rurban  |      Owner:  wyuenho
      Type:  defect  |     Status:  assigned
  Priority:  Normal  |  Milestone:
 Component:  ports   |    Version:
Resolution:          |   Keywords:  haspatch
      Port:  cquery  |
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Comment (by wyuenho):

 I feel like this patch should be submitted upstream, and guarded by some
 preprocessor constants so only systems that don't support C++14 will
 revert back to the slower mutex.

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Ticket URL: <https://trac.macports.org/ticket/57109#comment:4>
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