Big work-in-progress refactoring of the constraint solver:

1) Add fast branchless SIMD support for constraint solver (Windows only until we get other contributions).
See resolveSingleConstraintRowGenericSIMD in Bullet/src/BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.cpp
resolveSingleConstraintRowGenericSIMD can be used for all constraints, including contact, point 2 point, hinge, generic etc.

2) During this refactoring, all constraints support the obsolete 'solveConstraintObsolete' while we add 'getInfo1' and 'getInfo2' support.
This interface is almost identical interface to Open Dynamics Engine, to make it easier to port Dantzig LCP solver.

3) Some minor refactoring to reduce huge constructor overhead in math classes.

Demos/MultiThreadedDemo/MultiThreadedDemo.cpp

@@ -102,7 +102,7 @@ void MultiThreadedDemo::createStack( btCollisionShape* boxShape, float halfCubeS
 		int rowSize = size - i;
 		for(int j=0; j< rowSize; j++)
 		{
-			btVector4 pos;
+			btVector3 pos;
 			pos.setValue(
 				-rowSize * halfCubeSize + halfCubeSize + j * 2.0f * halfCubeSize,
 				halfCubeSize + i * halfCubeSize * 2.0f,
@@ -148,9 +148,10 @@ void MultiThreadedDemo::clientMoveAndDisplay()
 	if (m_dynamicsWorld)
 	{
 
-//#define FIXED_STEP 1
+#define FIXED_STEP 1
 #ifdef FIXED_STEP
   		m_dynamicsWorld->stepSimulation(1.0f/60.f,0);
+		//CProfileManager::dumpAll();
 	
 #else
 		//during idle mode, just run 1 simulation step maximum
@@ -354,6 +355,7 @@ m_threadSupportCollision = new Win32ThreadSupport(Win32ThreadSupport::Win32Threa
 		m_dynamicsWorld = world;
 
 		world->getSolverInfo().m_numIterations = 4;
+		world->getSolverInfo().m_solverMode = SOLVER_SIMD+SOLVER_USE_WARMSTARTING;
 
 		m_dynamicsWorld->getDispatchInfo().m_enableSPU = true;
 		m_dynamicsWorld->setGravity(btVector3(0,-10,0));