[MacPorts] #56294: boost: update to 1.70.0

[MacPorts]

#56294: boost: update to 1.70.0
------------------------+---------------------------------
  Reporter:  michaelld  |      Owner:  ryandesign
      Type:  update     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:  haspatch maintainer
      Port:  boost      |
------------------------+---------------------------------

Comment (by michaelld):

 I've fixed `gnuradio-next` to work with this Boost, and have pushed the
 fix to an upstream PR. I need to start adding rev-bumps of compatible
 ports to the WIP PR listed above.

-- 
Ticket URL: <https://trac.macports.org/ticket/56294#comment:31>
MacPorts <https://www.macports.org/>
Ports system for macOS