Hi Tom,
this patch removes large portions of plugin/plugin-nvptx.c, since a lot of it is
now in oacc-async.c now. The new code is essentially a NVPTX/CUDA-specific implementation
of the new-style goacc_asyncqueues.

Also, some needed functions in cuda-lib.def are added. The cuda.h function has also
been updated to build independently without a CUDA installation.

Thanks,
Chung-Lin

	* plugin/plugin-nvptx.c (struct cuda_map): Remove.
	(struct ptx_stream): Remove.
	(struct nvptx_thread): Remove current_stream field.
	(cuda_map_create): Remove.
	(cuda_map_destroy): Remove.
	(map_init): Remove.
	(map_fini): Remove.
	(map_pop): Remove.
	(map_push): Remove.
	(struct goacc_asyncqueue): Define.
	(struct nvptx_callback): Define.
	(struct ptx_free_block): Define.
	(struct ptx_device): Remove null_stream, active_streams, async_streams,
	stream_lock, and next fields.
	(enum ptx_event_type): Remove.
	(struct ptx_event): Remove.
	(ptx_event_lock): Remove.
	(ptx_events): Remove.
	(init_streams_for_device): Remove.
	(fini_streams_for_device): Remove.
	(select_stream_for_async): Remove.
	(nvptx_init): Remove ptx_events and ptx_event_lock references.
	(nvptx_attach_host_thread_to_device): Remove CUDA_ERROR_NOT_PERMITTED
	case.
	(nvptx_open_device): Add free_blocks initialization, remove
	init_streams_for_device call.
	(nvptx_close_device): Remove fini_streams_for_device call, add
	free_blocks destruct code.
	(event_gc): Remove.
	(event_add): Remove.
	(nvptx_exec): Adjust parameters and code.
	(nvptx_free): Likewise.
	(nvptx_host2dev): Remove.
	(nvptx_dev2host): Remove.
	(nvptx_set_async): Remove.
	(nvptx_async_test): Remove.
	(nvptx_async_test_all): Remove.
	(nvptx_wait): Remove.
	(nvptx_wait_async): Remove.
	(nvptx_wait_all): Remove.
	(nvptx_wait_all_async): Remove.
	(nvptx_get_cuda_stream): Remove.
	(nvptx_set_cuda_stream): Remove.
	(GOMP_OFFLOAD_alloc): Adjust code.
	(GOMP_OFFLOAD_free): Likewise.
	(GOMP_OFFLOAD_openacc_register_async_cleanup): Remove.
	(GOMP_OFFLOAD_openacc_exec): Adjust parameters and code.
	(GOMP_OFFLOAD_openacc_async_test_all): Remove.
	(GOMP_OFFLOAD_openacc_async_wait): Remove.
	(GOMP_OFFLOAD_openacc_async_wait_async): Remove.
	(GOMP_OFFLOAD_openacc_async_wait_all): Remove.
	(GOMP_OFFLOAD_openacc_async_wait_all_async): Remove.
	(GOMP_OFFLOAD_openacc_async_set_async): Remove.
	(cuda_free_argmem): New function.
	(GOMP_OFFLOAD_openacc_async_exec): New plugin hook function.
	(GOMP_OFFLOAD_openacc_create_thread_data): Adjust code.
	(GOMP_OFFLOAD_openacc_cuda_get_stream): Adjust code.
	(GOMP_OFFLOAD_openacc_cuda_set_stream): Adjust code.
	(GOMP_OFFLOAD_openacc_async_construct): New plugin hook function.
	(GOMP_OFFLOAD_openacc_async_destruct): New plugin hook function.
	(GOMP_OFFLOAD_openacc_async_test): Remove and re-implement.
	(GOMP_OFFLOAD_openacc_async_synchronize): New plugin hook function.
	(GOMP_OFFLOAD_openacc_async_serialize): New plugin hook function.
	(GOMP_OFFLOAD_openacc_async_queue_callback): New plugin hook function.
	(cuda_callback_wrapper): New function.
	(cuda_memcpy_sanity_check): New function.
	(GOMP_OFFLOAD_host2dev): Remove and re-implement.
	(GOMP_OFFLOAD_dev2host): Remove and re-implement.
	(GOMP_OFFLOAD_openacc_async_host2dev): New plugin hook function.
	(GOMP_OFFLOAD_openacc_async_dev2host): New plugin hook function.