Guard the debug exit(0) in the merge sort test from normal compilation.
Guard the debug exit(0) in the merge sort test from normal compilation.

--HG--
extra : convert_revision : svn%3A83215879-3e5a-4751-8c9d-778f44bb06a5/trunk%40780

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