Make BulletSim thread be ThreadPriority.Highest if running

Will only effect Windows or mono with a patch such as https://gist.github.com/justincc/31e52218d098529b4696 applied
For test purposes

OpenSim/Region/Physics/BulletSPlugin/BSScene.cs

@@ -838,6 +838,8 @@ public sealed class BSScene : PhysicsScene, IPhysicsParameters
 
     public void BulletSPluginPhysicsThread()
     {
+        Thread.CurrentThread.Priority = ThreadPriority.Highest;
+
         while (m_initialized)
         {
             int beginSimulationRealtimeMS = Util.EnvironmentTickCount();