Fix #2768 - remove completed timers

src/timer.h

@@ -3,16 +3,17 @@
 #include "arch.h"
 
 struct mg_timer {
-  unsigned long id;         // Timer ID
-  uint64_t period_ms;       // Timer period in milliseconds
-  uint64_t expire;          // Expiration timestamp in milliseconds
-  unsigned flags;           // Possible flags values below
-#define MG_TIMER_ONCE 0     // Call function once
-#define MG_TIMER_REPEAT 1   // Call function periodically
-#define MG_TIMER_RUN_NOW 2  // Call immediately when timer is set
-  void (*fn)(void *);       // Function to call
-  void *arg;                // Function argument
-  struct mg_timer *next;    // Linkage
+  uint64_t period_ms;          // Timer period in milliseconds
+  uint64_t expire;             // Expiration timestamp in milliseconds
+  unsigned flags;              // Possible flags values below
+#define MG_TIMER_ONCE 0        // Call function once
+#define MG_TIMER_REPEAT 1      // Call function periodically
+#define MG_TIMER_RUN_NOW 2     // Call immediately when timer is set
+#define MG_TIMER_CALLED 4      // Timer function was called at least once
+#define MG_TIMER_AUTODELETE 8  // free() timer when done
+  void (*fn)(void *);          // Function to call
+  void *arg;                   // Function argument
+  struct mg_timer *next;       // Linkage
 };
 
 void mg_timer_init(struct mg_timer **head, struct mg_timer *timer,