corrected use of specific bit-length types to use universal types

as per Apple's 64-bit conversion guide - https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Cocoa64BitGuide/ConvertingExistingApp/ConvertingExistingApp.html
Merge pull request #108 from BillinghamJ/master

corrected use of specific bit-length types to use universal types