Add empty() function
Add empty() function

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