[MacPorts] #50671: boost: Update to 1.64.0

[MacPorts]

#50671: boost: Update to 1.64.0
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  Reporter:  eborisch  |      Owner:  ryandesign
      Type:  update    |     Status:  new
  Priority:  Normal    |  Milestone:
 Component:  ports     |    Version:  2.3.4
Resolution:            |   Keywords:  haspatch
      Port:  boost     |
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Comment (by michaelld):

 Boost 1.64.0 is out. In my initial testing, the only required changes from
 1.63.0 are the version & checksums; there are a few patch tweaks to get
 them clean, but they do work.

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Ticket URL: <https://trac.macports.org/ticket/50671#comment:32>
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