* params.def (PARAM_MAX_LTO_STREAMING_PARALLELISM): New parameter.
	* lto.c (do_stream_out): rename to ...
	(stream_out): ... this one; move original code to ...
	(stream_out_partitions_1, stream_out_partitions): ... these new
	functions.
	(lto_wpa_write_files): Honnor lto_parallelism

From-SVN: r270317