[MacPorts] #51453: Update CImg to 1.7.1

[MacPorts]

#51453: Update CImg to 1.7.1
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 Reporter:  bstj@…  |      Owner:  macports-tickets@…
     Type:  update  |     Status:  new
 Priority:  Normal  |  Milestone:
Component:  ports   |    Version:  2.3.4
 Keywords:          |       Port:  CImg
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Ticket URL: <https://trac.macports.org/ticket/51453>
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