UtilSourceBytes and Strings
In 4.02.0, s.[i] <- c becomes deprecated and this is very frustrating for CamlImages.
We introduce (<<) and replace them by s << i & c.
equivalent with Bytes.set
equivalent with Bytes.unsafe_set
range_check bs from to_ raises Invalid_argument "index out of bounds" when from and to_ are invalid range for bs.
equivalent with Array.unsafe.get
s @% p = Char.code @@ Bytes.get s p