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/PrefixScanHost.inl

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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
+
+
+template<>
+class PrefixScan<TYPE_HOST> : public PrefixScanBase
+{
+	public:
+		struct Data
+		{
+			Option m_option;
+		};
+
+		static
+		Data* allocate(const Device* deviceData, int maxSize, Option option = EXCLUSIVE)
+		{
+			ADLASSERT( deviceData->m_type == TYPE_HOST );
+
+			Data* data = new Data;
+			data->m_option = option;
+			return data;
+		}
+
+		static
+		void deallocate(Data* data)
+		{
+			delete data;
+		}
+
+		static
+		void execute(Data* data, Buffer<u32>& src, Buffer<u32>& dst, int n, u32* sum = 0)
+		{
+			ADLASSERT( src.getType() == TYPE_HOST && dst.getType() == TYPE_HOST );
+			HostBuffer<u32>& hSrc = (HostBuffer<u32>&)src;
+			HostBuffer<u32>& hDst = (HostBuffer<u32>&)dst;
+
+			u32 s = 0;
+			if( data->m_option == EXCLUSIVE )
+			{
+				for(int i=0; i<n; i++)
+				{
+					hDst[i] = s;
+					s += hSrc[i];
+				}
+			}
+			else
+			{
+				for(int i=0; i<n; i++)
+				{
+					s += hSrc[i];
+					hDst[i] = s;
+				}
+			}
+
+			if( sum )
+			{
+				*sum = hDst[n-1];
+			}
+		}
+
+
+};