Implement circular print buffer.

Implement circular print buffer.

2019-03-18  Andrew Stubbs  <ams@codesourcery.com>

	gcc/
	* config/gcn/gcn-run.c (struct output): Make next_output unsigned.
	Extend queue to 1024 entries.
	Add "consumed" field.
	(gomp_print_output): Remove print_index parameter.
	Add final parameter.
	Change limit to unsigned.
	Use consumed field to implement circular buffer.
	Detect interrupted print in final pass.
	Flush output at the end.
	(run): Update gomp_print_output usage.
	(main): Initialize kernargs->output_data.consumed.

From-SVN: r269764