Added btCudaBroadphase, some early research & development work to accelerate Bullet using CUDA

Re-uses the NVidia particle demo.

Extras/CUDA/particleSystem.cuh

@@ -0,0 +1,57 @@
+extern "C"
+{
+void cudaInit(int argc, char **argv);
+
+void allocateArray(void **devPtr, int size);
+void freeArray(void *devPtr);
+
+void threadSync();
+
+void copyArrayFromDevice(void* host, const void* device, unsigned int vbo, int size);
+void copyArrayToDevice(void* device, const void* host, int offset, int size);
+void registerGLBufferObject(unsigned int vbo);
+void unregisterGLBufferObject(unsigned int vbo);
+
+void setParameters(SimParams *hostParams);
+
+void 
+integrateSystem(uint vboOldPos, uint vboNewPos, 
+                float* oldVel, float* newVel, 
+                float deltaTime,
+                int numBodies);
+
+void 
+updateGrid(uint    vboPos, 
+           uint*   gridCounters,
+           uint*   gridCells,
+           uint    numBodies,
+           uint    numCells);
+
+void 
+calcHash(uint    vboPos, 
+         uint*   particleHash,
+         int     numBodies);
+
+void 
+reorderDataAndFindCellStart(uint*  particleHash,
+							uint   vboOldPos,
+							float* oldVel,
+							float* sortedPos,
+							float* sortedVel,
+							uint*  cellStart,
+							uint   numBodies,
+							uint   numCells);
+
+void
+collide(uint   vboOldPos, uint vboNewPos,
+        float* sortedPos, float* sortedVel,
+        float* oldVel, float* newVel,
+        uint*  gridCounters,
+        uint*  gridCells,
+        uint*  particleHash,
+        uint*  cellStart,
+        uint   numBodies,
+        uint   numCells,
+        uint   maxParticlesPerCell);
+
+}