Clean up libgomp GCC 5 legacy support

	libgomp/
	* oacc-parallel.c: Add comments to legacy entry points (GCC 5).

From-SVN: r270901

libgomp/ChangeLog

+2019-05-06  Thomas Schwinge  <thomas@codesourcery.com>
+
+	* oacc-parallel.c: Add comments to legacy entry points (GCC 5).
+
 2019-03-27  Kevin Buettner  <kevinb@redhat.com>
 
 	* team.c (gomp_team_start): Initialize pool->threads[0].

libgomp/oacc-parallel.c

@@ -275,7 +275,7 @@ GOACC_parallel_keyed (int flags_m, void (*fn) (void *),
   acc_dev->openacc.async_set_async_func (acc_async_sync);
 }
 
-/* Legacy entry point, only provide host execution.  */
+/* Legacy entry point (GCC 5).  Only provide host fallback execution.  */
 
 void
 GOACC_parallel (int flags_m, void (*fn) (void *),
@@ -649,12 +649,16 @@ GOACC_wait (int async, int num_waits, ...)
     acc_wait_all_async (async);
 }
 
+/* Legacy entry point (GCC 5).  */
+
 int
 GOACC_get_num_threads (void)
 {
   return 1;
 }
 
+/* Legacy entry point (GCC 5).  */
+
 int
 GOACC_get_thread_num (void)
 {