Added an osgDB::ReadWriteMutex to help manage the ability to have serialize

write to objects but allow multiple threads to read at once in a read only way.

include/osgParticle/ParticleProcessor

@@ -171,8 +171,6 @@ namespace osgParticle
         //added- 1/17/06- bgandere@nps.edu 
         //a var to keep from doing multiple updates
         int _frameNumber;
-        
-        OpenThreads::Mutex _cullUpdatelMutex;
     };
     
     // INLINE FUNCTIONS