removed obsoletes
	deleted:    ps/builtins.go
	deleted:    ps/parse.go
	deleted:    ps/parse_test.go
	deleted:    ps/scheme.go
	deleted:    ps/scheme_test.go
	deleted:    ps/tokenize.go
	deleted:    ps/tokenize_test.go
	deleted:    ps/util.go
	deleted:    ps/util_test.go