Various improvements to example task systems in examples/.

- Only have a single copy of all of the tasks_*.cpp sample implementations,
  stored in examples/.
- Reduce dynamic storage allocation and locking in task launch code paths.
- Don't have a hard limit of the number of tasks that can be launched on
  Windows (fix issue #85).

examples/volume_rendering/volume.cpp

@@ -174,9 +174,6 @@ int main(int argc, char *argv[]) {
 
     ensureTargetISAIsSupported();
 
-    extern void TasksInit();
-    TasksInit();
-    
     //
     // Load viewing data and the volume density data
     //