added 5 new functions (sixth, seventh..)

stdlib/stdlib.lsp

@@ -54,6 +54,11 @@
 (defun third (l) (index l 2))
 (defun fourth (l) (index l 3))
 (defun fifth (l) (index l 4))
+(defun sixth (l) (index l 5))
+(defun seventh (l) (index l 6))
+(defun eight (l) (index l 7))
+(defun nineth (l) (index l 8))
+(defun tenth (l) (index l 9))
 (defun nth (i l) (index l (- i 1)))
 
 ; return 1 when list contains item otherwise 0