[MacPorts] #31319: msgpack: update to 0.5.7

[MacPorts]

#31319: msgpack: update to 0.5.7
-------------------------------------+--------------------------------------
 Reporter:  ryandesign@…             |       Owner:  naoya.n@…        
     Type:  update                   |      Status:  new              
 Priority:  Normal                   |   Milestone:                   
Component:  ports                    |     Version:  2.0.3            
 Keywords:  haspatch                 |        Port:  msgpack          
-------------------------------------+--------------------------------------
 msgpack should probably be updated to 0.5.7. Here's a patch. Let me know
 if it looks ok and I can commit it.

-- 
Ticket URL: <https://trac.macports.org/ticket/31319>
MacPorts <http://www.macports.org/>
Ports system for Mac OS