Common::MacResMan is now able to open files from a specified
Common::Archive. This is a bit hacky as dynamic_cast is used to break
the Archive encapsulation to retreive the underlying FSNode. It should
however be more correct than the previous code that assumed files were
at the root of the currently running game's path.
AdvancedDetector constructs a Common::Archive from its FileMap based
filesystem cache and uses it to detect the mac resource fork files.
This cuts the time it takes to run the detection code with all the
engines enabled as dynamic plugins on the 3DS to 30 s from 280 s.