Rename cuda_vector tests.

diff --git a/tests/cuda/cuda_vector_01.cc b/tests/cuda/cuda_vector_01.cu
similarity index 100%
rename from tests/cuda/cuda_vector_01.cc
rename to tests/cuda/cuda_vector_01.cu

diff --git a/tests/cuda/cuda_vector_02.cc b/tests/cuda/cuda_vector_02.cu
similarity index 100%
rename from tests/cuda/cuda_vector_02.cc
rename to tests/cuda/cuda_vector_02.cu