Parallel: wait for all ths to die

Former-commit-id: d95a5fc60c424cb1722d70ced610a81237ddb681
Former-commit-id: 64d1177a164a2a53e9beabe634a6f5997cfa8d7b

src/net/torvald/terrarum/concurrent/ThreadParallel.kt

@@ -25,6 +25,14 @@ object ThreadParallel {
         pool.forEach { it?.start() }
     }
 
+    /**
+     * Start all thread in the pool and wait for them to all die. If the thread in the pool is NULL, it will simply ignored.
+     */
+    fun startAllWaitForDie() {
+        pool.forEach { it?.start() }
+        pool.forEach { it?.join() }
+    }
+
     /**
      * Primitive locking
      */