[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 michaelld):

 Thanks for working on this @macsguy! I have no issues sharing
 maintainership of Boost and very likely a bunch of Boost versions. As
 noted: So long as they all install in parallel and we can coerce dependent
 ports to use the correct one, then this setup can be made to work. Very
 much like the Qt ports. Folks have complained over the years about the
 lack of default, but thus far we've been able to make everything work well
 enough & that's the bottom line :)

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Ticket URL: <https://trac.macports.org/ticket/59834#comment:25>
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