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/opengl_interop/interopKernel.cl

@@ -0,0 +1,13 @@
+MSTRINGIFY(
+
+__kernel void 
+interopKernel( const int startOffset, const int numNodes, __global float *g_vertexBuffer)
+{
+	int nodeID = get_global_id(0);
+	if( nodeID < numNodes )
+	{
+		g_vertexBuffer[nodeID*4 + startOffset+1] += 0.01;
+	}
+}
+
+);