PkgInfo stores type code and creator code, and something is inherited from Mac OS Classic.
Does this file have any purpose en iOS?
The contents of the PkgInfo file are a 4-byte type of package, followed by a 4-byte signature for your application.
It comes with OS X, iOS does not require this file, and you do not need to do anything with it.
See the following: Book: IOS 6 Programming by Matt Neuburg
Apple Docs: https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPRuntimeConfig/Articles/ConfigApplications.html