Avoid warnings of overflow in the computation of xor_combine_engine::max Reported by Nick Kitten
Avoid warnings of overflow in the computation of xor_combine_engine::max
Reported by Nick Kitten

Fixes #142

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