[MacPorts] #59834: Boost: update to 1.72.0

[MacPorts]

#59834: Boost: update to 1.72.0
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 Reporter:  michaelld  |      Owner:  (none)
     Type:  update     |     Status:  new
 Priority:  Normal     |  Milestone:
Component:  ports      |    Version:
 Keywords:             |       Port:  boost
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 Boost 1.72.0 was released on 20191211. My initial testing shows 2 things:

 (1) the new API ''is'' compatible with every port I have installed that
 requires Boost --26 ports, out of the roughly 268 ports that `port echo
 depends:boost` returns -- so about 10%, which for my current setup --
 macOS 10.14.6 18G1012 / Xcode 11.2.1 11B500 -- all build cleanly & I saw
 no deprecation warnings in the build logs I reviewed (about 10 of those
 ports)!

 (2) The new ABI ''is not'' compatible with the prior one. Hence, we have
 to actually rev-bump ports to link against the new ABI.

 I'm going to create a PR for this update & post it here: first for Boost
 itself then rev-bumps for the dependent ports that I've tested. I'd
 encourage others to add to it.

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