[MacPorts] #57117: upgrade last users of protobuf-cpp to protobuf3-cpp

[MacPorts]

#57117: upgrade last users of protobuf-cpp to protobuf3-cpp
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  Reporter:  pmetzger                            |      Owner:  (none)
      Type:  enhancement                         |     Status:  new
  Priority:  Normal                              |  Milestone:
 Component:  ports                               |    Version:
Resolution:                                      |   Keywords:
      Port:  caffe MyPaint opencv raceintospace  |
  shogun-devel sumo                              |
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Comment (by ryandesign):

 Yes. And the port that is using protobuf3-cpp should probably be asking
 protobuf3-cpp what flags it should be using to do that, such as by using
 pkg-config, right? I'm suggesting putting the flag in protobuf.pc (and
 protobuf-lite.pc if applicable).

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Ticket URL: <https://trac.macports.org/ticket/57117#comment:11>
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