Add missing documentation.
Add missing documentation.

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