Re-introduce GPU parallel Jacobi solver, called btGpuJacobiContactSolver. There are still some issues, but for basic scene's it works.

To avoid confusion, rename GPU contact solver to btGpuContactSolver, and constraint (non-contact) solver to btPgsConstraintSolver.

src/Bullet3OpenCL/RigidBody/b3GpuPgsContactSolver.h

@@ -0,0 +1,40 @@
+
+#ifndef B3_GPU_BATCHING_PGS_SOLVER_H
+#define B3_GPU_BATCHING_PGS_SOLVER_H
+
+#include "Bullet3OpenCL/Initialize/b3OpenCLInclude.h"
+#include "Bullet3OpenCL/ParallelPrimitives/b3OpenCLArray.h"
+#include "Bullet3Collision/NarrowPhaseCollision/b3RigidBodyCL.h"
+#include "Bullet3Collision/NarrowPhaseCollision/b3Contact4.h"
+#include "b3GpuConstraint4.h"
+
+class b3GpuPgsContactSolver
+{
+protected:
+
+	int m_debugOutput;
+
+	struct b3GpuBatchingPgsSolverInternalData*		m_data;
+
+	void batchContacts( b3OpenCLArray<b3Contact4>* contacts, int nContacts, b3OpenCLArray<unsigned int>* n, b3OpenCLArray<unsigned int>* offsets, int staticIdx );
+	
+	inline int sortConstraintByBatch( b3Contact4* cs, int n, int simdWidth , int staticIdx, int numBodies);
+	inline int sortConstraintByBatch2( b3Contact4* cs, int n, int simdWidth , int staticIdx, int numBodies);
+	inline int sortConstraintByBatch3( b3Contact4* cs, int n, int simdWidth , int staticIdx, int numBodies);
+	
+
+
+	void solveContactConstraint(  const b3OpenCLArray<b3RigidBodyCL>* bodyBuf, const b3OpenCLArray<b3InertiaCL>* shapeBuf, 
+			b3OpenCLArray<b3GpuConstraint4>* constraint, void* additionalData, int n ,int maxNumBatches, int numIterations);
+
+public:
+	
+	b3GpuPgsContactSolver(cl_context ctx,cl_device_id device, cl_command_queue  q,int pairCapacity);
+	virtual ~b3GpuPgsContactSolver();
+
+	void solveContacts(int numBodies, cl_mem bodyBuf, cl_mem inertiaBuf, int numContacts, cl_mem contactBuf, const struct b3Config& config, int static0Index);
+
+};
+
+#endif //B3_GPU_BATCHING_PGS_SOLVER_H
+