Provide a forward declaration for raw_cuda_device_buffer in cuda/copy_if.inl to fix broken trivial tests.
Provide a forward declaration for raw_cuda_device_buffer in cuda/copy_if.inl to fix broken trivial tests.

thrust/thrust,xiongzhanblake/thrust_src,Ricardo666666/thrust,marksantos/thrust,sarvex/thrust,raygit/thrust,xiongzhanblake/thrust,egaburov/thrust,andrewcorrigan/thrust-multi-permutation-iterator,mohamed-ali/thrust,thvasilo/thrust,egaburov/thrust,arnabgho/thrust,zeryx/thrust,raygit/thrust,marksantos/thrust,zhenglaizhang/thrust,thrust/thrust,dachziegel/thrust,arnabgho/thrust,jaredhoberock/thrust,thrust/thrust,GrimDerp/thrust,thrust/thrust,sdalton1/thrust,andrewcorrigan/thrust-multi-permutation-iterator,mohamed-ali/thrust,sdalton1/thrust,GrimDerp/thrust,raygit/thrust,thvasilo/thrust,GrimDerp/thrust,zhenglaizhang/thrust,jaredhoberock/thrust,Ricardo666666/thrust,Ricardo666666/thrust,marksantos/thrust,sarvex/thrust,zeryx/thrust,jaredhoberock/thrust,zeryx/thrust,thrust/thrust,jaredhoberock/thrust,zhenglaizhang/thrust,xiongzhanblake/thrust,sdalton1/thrust,xiongzhanblake/thrust_src,thvasilo/thrust,dachziegel/thrust,egaburov/thrust,andrewcorrigan/thrust-multi-permutation-iterator,jaredhoberock/thrust,sarvex/thrust,dachziegel/thrust,arnabgho/thrust,xiongzhanblake/thrust,xiongzhanblake/thrust_src,mohamed-ali/thrust