[ci skip] Add interface for {In,Out}_channel

stdlib/in_channel.mli

@@ -0,0 +1,35 @@
+type t = in_channel
+
+val stdin : t
+
+val create : string -> t
+
+val create_bin : string -> t
+
+val create_gen : open_flag list -> t
+
+val seek : t -> int64 -> unit
+
+val pos : t -> int64
+
+val length : t -> int64
+
+val close : t -> unit
+
+val close_noerr : t -> unit
+
+val input_byte : t -> int option
+
+val input_char : t -> char option
+
+val input_line : t -> string option
+
+val input_binary_int : t -> int option
+
+val input : t -> bytes -> int -> int -> int
+
+val really_input : t -> bytes -> int -> int -> unit option
+
+val really_input_string : t -> int -> string option
+
+val set_binary_mode : t -> bool -> unit

stdlib/out_channel.mli

@@ -0,0 +1,41 @@
+type t = out_channel
+
+val stdout : t
+
+val stderr : t
+
+val create : string -> t
+
+val create_bin : string -> t
+
+val create_gen : open_flag list -> string -> t
+
+val seek : t -> int64 -> unit
+
+val pos : t -> int64
+
+val length : t -> int64
+
+val close : t -> unit
+
+val close_noerr : t -> unit
+
+val flush : t -> unit
+
+val flush_all : unit -> unit
+
+val output_byte : t -> int -> unit
+
+val output_char : t -> char -> unit
+
+val output_string : t -> string -> unit
+
+val output_bytes : t -> bytes -> unit
+
+val output : t -> bytes -> int -> int -> unit
+
+val output_substring : t -> string -> int -> int -> unit
+
+val output_binary_int : t -> int -> unit
+
+val set_binary_mode : t -> bool -> unit