[MacPorts] #55092: meld: bump to 3.18.0 (python3)

[MacPorts]

#55092: meld: bump to 3.18.0 (python3)
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  Reporter:  elelay  |      Owner:
      Type:  update  |     Status:  new
  Priority:  Normal  |  Milestone:
 Component:  ports   |    Version:
Resolution:          |   Keywords:  haspatch
      Port:  meld    |
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Comment (by mf2k):

 Please just support the latest python 3.6 and remove the older versions. I
 can test it on High Sierra.

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Ticket URL: <https://trac.macports.org/ticket/55092#comment:1>
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