Eliminate unused variable warnings in testing/discard_iterator.cu
Eliminate unused variable warnings in testing/discard_iterator.cu

Fixes #102

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