synchronized multithreaded message list updates

- Avoids inaccuracies when tasks are delayed.
- More testing required to remove all crashes.

Author: Michael Farb

safeslinger-messenger/AndroidManifest.xml

@@ -26,7 +26,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="edu.cmu.cylab.starslinger"
     android:versionCode="0x01080102"
-    android:versionName="1.8.1.2 PostRegistration Tests" >
+    android:versionName="1.8.1.2 RC 0" >
 
     <!-- API 9 is the minimum required for password-based encryption PBKDF2WithHmacSHA1. -->
     <!-- API 9 is the minimum required to receive GCM push messages. -->