Make fill_functor's member be non-const so a copy constructor can be generated.
Make fill_functor's member be non-const so a copy constructor can be generated.

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