xbps-bin: implement full support for the 'show' target.

This will try to show the package information by looking in
all repositories registered. The first one that has the package
info wins.

--HG--
extra : convert_revision : 33b93fd115a765d696af76ca20c1669ef277cd35

utils/xbps-pkgdb.c

@@ -292,7 +292,7 @@ main(int argc, char **argv)
 
 		dbdict = prop_dictionary_internalize_from_file(dbfile);
 		if (!xbps_callback_array_iter_in_dict(dbdict,
-		    "packages", xbps_list_pkgs_in_dict))
+		    "packages", xbps_list_pkgs_in_dict, NULL))
 			exit(EINVAL);
 
 	} else if (strcmp(argv[1], "version") == 0) {