[MacPorts] #51310: ImageMagick: update to 7.x

[MacPorts]

#51310: ImageMagick: update to 7.x
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  Reporter:  mopihopi     |      Owner:  ryandesign
      Type:  update       |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  ImageMagick  |
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Comment (by diekhans):

 Could this be done as a fork?  Update the port file in the fork, and then
 those of us watching can take on modifying dependent packages.  I am not
 versed in MacPorts development, but I can get software to compile and do
 pull requests.

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Ticket URL: <https://trac.macports.org/ticket/51310#comment:67>
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