make accessible to the end user the number of available connections

src/Tiny_httpd.ml

@@ -870,6 +870,9 @@ type t = {
 let addr self = self.addr
 let port self = self.port
 
+let available_connections self =
+  Sem_.available_connections self.sem_max_connections
+
 let add_decode_request_cb self f =  self.cb_decode_req <- f :: self.cb_decode_req
 let add_encode_response_cb self f = self.cb_encode_resp <- f :: self.cb_encode_resp
 let set_top_handler self f = self.handler <- f

src/Tiny_httpd.mli

@@ -477,6 +477,9 @@ val is_ipv6 : t -> bool
 val port : t -> int
 (** Port on which the server listens. *)
 
+val available_connections : t -> int
+(** number of available connections on the server. *)
+
 val add_decode_request_cb :
   t ->
   (unit Request.t -> (unit Request.t * (byte_stream -> byte_stream)) option) -> unit