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.

src/LinearMath/btQuaternion.h

@@ -19,6 +19,7 @@ subject to the following restrictions:
 
 
 #include "btVector3.h"
+#include "btQuadWord.h"
 
 /**@brief The btQuaternion implements quaternion to perform linear algebra rotations in combination with btMatrix3x3, btVector3 and btTransform. */
 class btQuaternion : public btQuadWord {