add CCstring.of_char

src/core/CCString.cppo.ml

@@ -475,6 +475,8 @@ let _to_gen s i0 len =
 
 let to_gen s = _to_gen s 0 (String.length s)
 
+let of_char c = String.make 1 c
+
 let of_gen g =
   let b = Buffer.create 32 in
   let rec aux () = match g () with

src/core/CCString.mli

@@ -94,6 +94,10 @@ val pad : ?side:[`Left|`Right] -> ?c:char -> int -> string -> string
   "aaa" (pad ~side:`Right ~c:'a' 3 "")
 *)
 
+val of_char : char -> string
+(** [of_char 'a' = "a"]
+    @since NEXT_RELEASE *)
+
 val of_gen : char gen -> string
 val of_seq : char sequence -> string
 val of_klist : char klist -> string