Fixed issue #114 - There are still iOS 6 dispatch_get_current_queue warnings in GCDAsyncUdpSocket.m

Used the same approach as in ef08e460756b391dd2fdd78d3133b1403f7671e1
Merge pull request #129 from mgratzer/master

Fixes the iOS6 dispatch_get_current_queue() warnings in GCDAsyncUdpSocket.m