MusicKit 5.5.2 Released

The major features of this release is to enable compilation on MacOS 10.4.0 with Xcode 2.0 and the finicky gcc 4.0. There are a few warnings which are now generated, but the reason for not fixing them is those offending regions of the code are marked for modification anyway.

The framework (i.e API) documentation has also been converted from headerdoc to doxygen, which is much better supported. Doxygen has a C++ terminology which I've yet to discover if it can be tuned to use Objective-C terms. Documentation building is now incorporated into the Xcode and make build processes. There are still a number of warnings which are generated when running doxygen, but due to the error format of doxygen matching gcc, they can be inspected and fixed with Xcode.

Packaging of binaries has been completely overhauled so this should speed up releasing future versions.