Support autojit-device function and cuda.jit as cuda.autojit

See https://github.com/sklam/numba/blob/cuda_autojit_device/numba/cuda/tests/cudapy/test_cuda_autojit.py#L26 for example of the added feature
In this branch the inline kwarg appears to be ignored - presumably it is not forced to be inline? Should the user be warned in this situation?