[MacPorts] #50671: boost: Update to 1.60.0

[MacPorts]

#50671: boost: Update to 1.60.0
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 Reporter:  eborisch@…  |      Owner:  macports-tickets@…
     Type:  update      |     Status:  new
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:  2.3.4
 Keywords:  haspatch    |       Port:  boost
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 Portfile patch attached. Some of the patchfiles can go away, too.

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