[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 kencu):

 someone also has to do part B, to either co-install ImageMagick6 beside
 ImageMagick7, or at least install ImageMagick6 tucked away in
 {{{${prefix}/libexec}}}.

 then we upgrade to ImageMagick7, start revbumping everything that links
 against the libraries to rebuild them all, and if there are any left by
 this late date that won't work against ImageMagick7 (I seriously doubt it,
 but .... ) then figure out how to force them to use ImageMagick6 instead
 of ImageMagick7.

 I bet you could have this all done in 2 actual hours of coding.

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Ticket URL: <https://trac.macports.org/ticket/51310#comment:66>
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