use DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS by default for now,
until we find the issue with some failing test cases in btMultiBody
fix a crashing issue in MyMultiBodyCreator.cpp (uninitialized variable)
disable excessive debug printf in URDF2Bullet
Remove constructor from b3Vector3, to make it a POD type, so it can go into a union (and more compatible with OpenCL float4)
Use b3MakeVector3 instead of constructor
Share some code between C++ and GPU in a shared file: see b3TransformAabb2 in src/Bullet3Collision/BroadPhaseCollision/shared/b3Aabb.h
Improve PairBench a bit, show timings and #overlapping pairs.
Increase shadowmap default size to 8192x8192 (hope the GPU supports it)
