Test string slicing

tests/all.test

@@ -178,6 +178,10 @@ null
 [0,1,2,3,4,5,6]
 [[], [2,3], [0,1,2,3,4], [5,6], [], []]
 
+[.[3:2], .[-5:4], .[:-2], .[-2:], .[3:3][1:], .[10:]]
+"abcdefghi"
+["","","abcdefg","hi","",""]
+
 del(.[2:4],.[0],.[-2:])
 [0,1,2,3,4,5,6,7]
 [1,4,5]