Add the GPU rigid body pipeline from https://github.com/erwincoumans/experiments as a Bullet 3.x preview for Bullet 2.80

Extras/RigidBodyGpuPipeline/opencl/primitives/AdlPrimitives/Scan/PrefixScan.h

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+/*
+Copyright (c) 2012 Advanced Micro Devices, Inc.  
+
+This software is provided 'as-is', without any express or implied warranty.
+In no event will the authors be held liable for any damages arising from the use of this software.
+Permission is granted to anyone to use this software for any purpose, 
+including commercial applications, and to alter it and redistribute it freely, 
+subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+*/
+//Originally written by Takahiro Harada
+
+#pragma once
+
+#include <Adl/Adl.h>
+#include <AdlPrimitives/Math/Math.h>
+
+namespace adl
+{
+
+class PrefixScanBase
+{
+	public:
+		enum Option
+		{
+			INCLUSIVE, 
+			EXCLUSIVE
+		};
+};
+
+
+template<DeviceType TYPE>
+class PrefixScan : public PrefixScanBase
+{
+	public:
+		typedef Launcher::BufferInfo BufferInfo;
+
+		enum
+		{
+			BLOCK_SIZE = 128
+		};
+
+		struct Data
+		{
+			Option m_option;
+			const Device* m_device;
+			Kernel* m_localScanKernel;
+			Kernel* m_blockSumKernel;
+			Kernel* m_propagationKernel;
+			Buffer<u32>* m_workBuffer;
+			Buffer<int4>* m_constBuffer[3];// todo. dx need one for each
+			int m_maxSize;
+		};
+
+		static
+		Data* allocate(const Device* deviceData, int maxSize, Option option = EXCLUSIVE);
+
+		static
+		void deallocate(Data* data);
+
+		static
+		void execute(Data* data, Buffer<u32>& src, Buffer<u32>& dst, int n, u32* sum = 0);
+};
+
+
+
+#include <AdlPrimitives/Scan/PrefixScanHost.inl>
+#include <AdlPrimitives/Scan/PrefixScan.inl>
+
+};