[MacPorts] #50572: boost @1.59.0 Update to to 1.60.0

[MacPorts]

#50572: boost @1.59.0 Update to to 1.60.0
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  Reporter:  crmoore@…  |      Owner:  ryandesign@…
      Type:  update     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:
      Port:  boost      |
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Comment (by michaelld@…):

 W/r.t. the "-mt" extension: Maybe we can do the build without it, but add
 in symlinks to that name for a few iterations of Boost updates. So long as
 the self-id is without it, then usage will slowly migrate to not using it
 on user's systems. Maybe then at 1.62 we can remove it altogether; or
 something like that.

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Ticket URL: <https://trac.macports.org/ticket/50572#comment:7>
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