Manually encode voice messages to AAC with ADTS headers

Should resolve issues with platforms that don't support AMR (!).

Fixes #4640
Fixes #4652
Fixes #4647
// FREEBIE

src/org/thoughtcrime/securesms/util/ThreadUtil.java

@@ -0,0 +1,19 @@
+package org.thoughtcrime.securesms.util;
+
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+
+public class ThreadUtil {
+
+  public static ExecutorService newDynamicSingleThreadedExecutor() {
+    ThreadPoolExecutor executor = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS,
+                                                         new LinkedBlockingQueue<Runnable>());
+    executor.allowCoreThreadTimeOut(true);
+
+    return executor;
+  }
+
+}