jtk.timer: specify functions with package-only access

src/jtk/timer.d

@@ -27,7 +27,7 @@ class Timer
         timers.remove(this);
     }
 
-    void service()
+    package void service()
     {
         if (this.interval == 0u)
         {
@@ -39,7 +39,7 @@ class Timer
         }
     }
 
-    static Timer get_expired_timer()
+    package static Timer get_expired_timer()
     {
         ulong current_time = us_time();
         foreach (Timer timer; timers)
@@ -52,7 +52,7 @@ class Timer
         return null;
     }
 
-    static ulong time_to_next_timer_expiration()
+    package static ulong time_to_next_timer_expiration()
     {
         ulong rv = cast(ulong)-1;
         ulong current_time = us_time();