[openacc] Factor out async argument utility functions

[openacc] Factor out async argument utility functions

2018-05-09  Tom de Vries  <tom@codesourcery.com>

	PR libgomp/83792
	* oacc-int.h (async_valid_stream_id_p, async_valid_p)
	(async_synchronous_p): New function.
	* oacc-async.c (acc_async_test, acc_wait, acc_wait_all_async): Use
	async_valid_p.
	* oacc-cuda.c (acc_get_cuda_stream, acc_set_cuda_stream): Use
	async_valid_stream_id_p.
	* oacc-mem.c (gomp_acc_remove_pointer): Use async_synchronous_p.
	* oacc-parallel.c (GOACC_parallel_keyed): Same.

From-SVN: r260081