Fix instances where the depreciated Core.Caml is used.

Core.Caml is depreciated in favor of Core.Stdlib. In the cases here I just made
it use the Core equivalent functions instead of the ones from the Ocaml stdlib.

This fixes a bunch of compiler warns with new core and does not break users who
may still have the older version.

exercises/practice/word-count/.meta/example.ml

@@ -11,7 +11,7 @@ type position =
   | Start
   | End
 
-let quote_at s ~pos = 
+let quote_at s ~pos =
   let p = match pos with
   | Start -> 0
   | End -> String.length s - 1
@@ -20,12 +20,12 @@ let quote_at s ~pos =
 
 let word_count s =
   let s = String.map s ~f:normalize in
-  let split = 
+  let split =
     List.filter (String.split s ~on:' ') ~f:(Fn.non String.is_empty)
-    |> List.map ~f:(fun w -> 
+    |> List.map ~f:(fun w ->
       let len = String.length w in
-      if len >= 2 && quote_at w ~pos:Start && quote_at w ~pos:End 
-      then Caml.String.sub w 1 (len - 2)
+      if len >= 2 && quote_at w ~pos:Start && quote_at w ~pos:End
+      then String.sub w ~pos:1 ~len:(len - 2)
       else w)
   in
   List.fold ~init:(Map.empty (module String)) ~f:add_to_map split

test-generator/bin_test_gen/test_gen.ml

@@ -7,7 +7,7 @@ let command =
       let cwd =
         flag_optional_with_default_doc "w" string Sexp.of_string
           ~aliases:["--cwd"]
-          ~default:(Caml.Sys.getcwd ()) ~doc:"directory to assume as cwd"
+          ~default:(Core_unix.getcwd ()) ~doc:"directory to assume as cwd"
       and templates_folder =
         flag_optional_with_default_doc "t" string Sexp.of_string
           ~aliases:["--templates"]

test-generator/lib_generator/exercise.ml

@@ -20,7 +20,7 @@ let of_candidate ~(tpl: string) ~(out: string) (c: Exercise_candidate.t): t =
 let to_string (e: t): string =
   let print_description = function
     | None -> "None"
-    | Some d -> Caml.Printf.sprintf "%s" d
+    | Some d -> Printf.sprintf "%s" d
   in
   Printf.sprintf "ExerciseCandidate { name = \"%s\"; directory = \"%s\"; description = \"%s\"; canonical_data = %s; templates = %s }"
     e.name

test-generator/lib_generator/files.ml

@@ -31,7 +31,7 @@ let mkdir_if_not_present dir =
 
 let backup ~(base_folder: string) ~(slug: string) ~(contents: string): bool =
   mkdir_if_not_present base_folder;
-  let path = Caml.Filename.concat base_folder slug in
+  let path = Filename.concat base_folder slug in
   let matches_contents =
     Option.try_with (fun () -> In_channel.read_all path)
     |> Option.map ~f:(String.equal contents)
@@ -88,7 +88,7 @@ let read_file (p: string): (string, exn) Result.t =
   try
     let c = Stdio.In_channel.create p in
     while true do
-      Buffer.add_string b (Caml.input_line c);
+      Buffer.add_string b (In_channel.input_line_exn c);
       Buffer.add_char b '\n';
     done;
     failwith "unreachable"

test-generator/lib_generator/glob.ml

@@ -4,11 +4,11 @@ let split c s =
 	let len = String.length s in
 	let rec loop acc last_pos pos =
 		if pos = -1 then
-		Caml.String.sub s 0 last_pos :: acc
+		String.sub s ~pos:0 ~len:last_pos :: acc
 		else
 		if Char.equal (String.get s pos) c then
 			let pos1 = pos + 1 in
-			let sub_str = Caml.String.sub s pos1 (last_pos - pos1) in
+			let sub_str = String.sub s ~pos:pos1 ~len:(last_pos - pos1) in
 			loop (sub_str :: acc) pos (pos - 1)
 		else loop acc last_pos (pos - 1)
 	in
@@ -21,7 +21,7 @@ let find_substrings ?(start_point=0) substr x =
 		if len_x - i < len_s
 		then acc
 		else
-			if String.equal (Caml.String.sub x i len_s) substr
+			if String.equal (String.sub x ~pos:i ~len:len_s) substr
 			then aux (i::acc) (i + 1)
 			else aux acc (i + 1)
 	in