[MacPorts] #55926: boost: Add C++11 variant

[MacPorts]

#55926: boost: Add C++11 variant
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  Reporter:  michaelld    |      Owner:
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:  c++11, haspatch
      Port:  boost        |
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Comment (by michaelld):

 Since nobody seems to either care or be against moving Boost to requiring
 C++11, I'm going to "just do it".

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Ticket URL: <https://trac.macports.org/ticket/55926#comment:3>
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