Add timer ID attribute, for safe cleanup in the scripted environment

mongoose.h

@@ -795,6 +795,7 @@ void mg_log_set_fn(void (*logfunc)(unsigned char ch));
 
 
 struct mg_timer {
+  unsigned long id;         // Timer ID
   uint64_t period_ms;       // Timer period in milliseconds
   uint64_t prev_ms;         // Timestamp of a previous poll
   uint64_t expire;          // Expiration timestamp in milliseconds
@@ -1001,12 +1002,13 @@ struct mg_mgr {
   int dnstimeout;               // DNS resolve timeout in milliseconds
   bool use_dns6;                // Use DNS6 server by default, see #1532
   unsigned long nextid;         // Next connection ID
+  unsigned long timerid;        // Next timer ID
   void *userdata;               // Arbitrary user data pointer
   uint16_t mqtt_id;             // MQTT IDs for pub/sub
   void *active_dns_requests;    // DNS requests in progress
   struct mg_timer *timers;      // Active timers
-  void *priv;                   // Used by the experimental stack
-  size_t extraconnsize;         // Used by the experimental stack
+  void *priv;                   // Used by the MIP stack
+  size_t extraconnsize;         // Used by the MIP stack
 #if MG_ARCH == MG_ARCH_FREERTOS_TCP
   SocketSet_t ss;  // NOTE(lsm): referenced from socket struct
 #endif