Add this note about use of permutation_iterator in CUDA set_intersection.
Add this note about use of permutation_iterator in CUDA set_intersection.

--HG--
extra : convert_revision : svn%3A83215879-3e5a-4751-8c9d-778f44bb06a5/trunk%40821

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