[MacPorts] #28385: graphics/libpng upgrade version to 1.5.1

[MacPorts]

#28385: graphics/libpng upgrade version to 1.5.1
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 Reporter:  rmstonecipher@…             |       Owner:  rmstonecipher@…           
     Type:  update                      |      Status:  new                       
 Priority:  Normal                      |   Milestone:                            
Component:  ports                       |     Version:  1.9.2                     
 Keywords:                              |        Port:  libpng                    
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Comment(by ryandesign@…):

 I don't think we need to list in this ticket any new ports that declare
 dependencies on libpng; those can be found easily enough with grep. exact-
 image already declares it, and arb should have, and does, as of r75955. If
 you find a port not in the list above that uses libpng without declaring a
 dependency on it, instead of adding a note here to that effect, why not
 add the libpng dependency to the port? Then there will never again be the
 possibility of it being left out for future updates.

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Ticket URL: <https://trac.macports.org/ticket/28385#comment:6>
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