[darwinbuild] darwinxref changes

I've committed largely re-written version of darwinxref to CVS at proj/darwinbuild/darwinxref. Some of the major changes include: * NeXT-style property list support -- XML was illegible, but will still be supported. * Build plists now contain a dictionary of projects, not an array. -- Makes syntax more consistent with semantics. -- Improved viewing in the Property List Editor. * Dependency property is a dictionary of dependency types. -- Better organization of dependencies in the plist. * Plug-in architecture for build plist properties. -- Provide future and site-specific extensibility. -- Potential for integration with DarwinPorts. - Kevin