MultiThreaded Demo:

- fixing various race conditions throughout (usage of static vars, etc)
 - addition of a few lightweight mutexes (which are compiled out by default)
 - slight code rearrangement in discreteDynamicsWorld to facilitate multithreading
 - PoolAllocator::allocate() can now be called when pool is full without
     crashing (null pointer returned)
 - PoolAllocator allocate and freeMemory, are OPTIONALLY threadsafe
     (default is un-threadsafe)
 - CollisionDispatcher no longer checks if the pool allocator is full
     before calling allocate(), instead it just calls allocate() and
     checks if the return is null -- this avoids a race condition
 - SequentialImpulseConstraintSolver OPTIONALLY uses different logic in
     getOrInitSolverBody() to avoid a race condition with kinematic bodies
 - addition of 2 classes which together allow simulation islands to be run
   in parallel:
    - btSimulationIslandManagerMt
    - btDiscreteDynamicsWorldMt
 - MultiThreadedDemo example in the example browser demonstrating use of
   OpenMP, Microsoft PPL, and Intel TBB
 - use multithreading for other demos
 - benchmark demo: add parallel raycasting

src/LinearMath/btConvexHull.cpp

@@ -87,7 +87,7 @@ btVector3  NormalOf(const btVector3 *vert, const int n);
 btVector3 PlaneLineIntersection(const btPlane &plane, const btVector3 &p0, const btVector3 &p1)
 {
 	// returns the point where the line p0-p1 intersects the plane n&d
-				static btVector3 dif;
+    btVector3 dif;
 		dif = p1-p0;
 				btScalar dn= btDot(plane.normal,dif);
 				btScalar t = -(plane.dist+btDot(plane.normal,p0) )/dn;
@@ -112,7 +112,7 @@ btVector3 TriNormal(const btVector3 &v0, const btVector3 &v1, const btVector3 &v
 
 btScalar DistanceBetweenLines(const btVector3 &ustart, const btVector3 &udir, const btVector3 &vstart, const btVector3 &vdir, btVector3 *upoint, btVector3 *vpoint)
 {
-	static btVector3 cp;
+	btVector3 cp;
 	cp = btCross(udir,vdir).normalized();
 
 	btScalar distu = -btDot(cp,ustart);