[MacPorts] #59834: Boost: update to 1.76.0

[MacPorts]

#59834: Boost: update to 1.76.0
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  Reporter:  michaelld  |      Owner:  mascguy
      Type:  update     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:
      Port:  boost      |
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Comment (by mascguy):

 Sounds good. As part of the effort, I'd also like to migrate away from
 python variants, to separate subports. This has worked well for other
 cases, like our OpenCV ports, and allow users to have Boost installed for
 multiple Python versions simultaneously.

 How does that sound? Your thoughts?

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Ticket URL: <https://trac.macports.org/ticket/59834#comment:26>
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