macosx_finder_args: use cocoa instead of carbon

macosx_finder_args: use cocoa instead of carbon

macosx_finder_args was using Carbon and wasn't usable any longer on
modern versions of MacOSX. This is very useful to embed mplayer in a
mac application bundle.

When using application bundles, the operating system will call the
main function with only one argument that identifies the process
serial number (this is some additional process identifier in osx other
than the pid). File open events are then dispatched to the application
through events that must be handled accordingly.