fixed multi GPU API, added driver_api prefix to multi gpu samples

modules/gpu/include/opencv2/gpu/gpu.hpp

@@ -138,6 +138,7 @@ namespace cv
         {
         public:
             MultiGpuMgr();
+            ~MultiGpuMgr();
 
             // Makes the given GPU active
             void gpuOn(int gpu_id);
@@ -148,8 +149,10 @@ namespace cv
             static const int BAD_GPU_ID = -1;
 
         private:
-            class Impl;
+            void operator=(const MultiGpuMgr&);
+            MultiGpuMgr(const MultiGpuMgr&);
 
+            class Impl;
             Ptr<Impl> impl_;
         };
 

modules/gpu/src/multi_gpu_mgr.cpp

@@ -117,6 +117,7 @@ MultiGpuMgr::Impl::Impl(): num_devices_(0)
 
 
 MultiGpuMgr::MultiGpuMgr(): impl_(new Impl()) {}
+MultiGpuMgr::~MultiGpuMgr() {}
 
 
 void MultiGpuMgr::gpuOn(int gpu_id)