Batteries user guide : BatUChar

`sig type t exception Out_of_range val char_of : BatUChar.t -> char val of_char : char -> BatUChar.t external code : BatUChar.t -> int = "%identity" val chr : int -> BatUChar.t val eq : BatUChar.t -> BatUChar.t -> bool val compare : BatUChar.t -> BatUChar.t -> int type uchar = BatUChar.t val int_of : BatUChar.uchar -> int val of_int : int -> BatUChar.uchar val is_ascii : BatUChar.uchar -> bool val unsafe_chr : int -> BatUChar.t end`