[MacPorts] #35884: optipng: version bump to 1.7.2

[MacPorts]

#35884: optipng: version bump to 1.7.2
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 Reporter:  khepler@…          |       Owner:  macports-tickets@…                   
     Type:  update             |      Status:  new                                  
 Priority:  Normal             |   Milestone:                                       
Component:  ports              |     Version:  2.1.2                                
 Keywords:                     |        Port:  optipng                              
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 OptiPNG current stable version is 1.7.2.  Tested on Leopard/PPC.

 Besides the version bump, the attached patch also includes the following:
 updated manpath handling, minor comment revision, and updated livecheck
 regex.

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Ticket URL: <https://trac.macports.org/ticket/35884>
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