Put dependencies in typelibs, resolve them when loading

	* gir/Makefile.am: Dep on Makefile
	* girepository/ginfo.c: Print out a nicer error
	message if we failed to load something.
	* girepository/girepository.c: Clean up
	default typelib handling; remove global
	default_typelib variable.  Ensure we handle
	NULL repository in more places.
	Support dependency resolution.
	* tests/Makefile.am: Kill off gobject.gir,
	it conflicts with the real one.
	* tests/Object.gir: Depend on GObject.
	* tools/generate.c: Take --includedir
	argument to say which directories to search
	for typelibs.  Print out dependencies.

svn path=/trunk/; revision=541