lto-streamer-out.c (DFS::DFS_write_tree_body): Process DECL_DEBUG_EXPR conditional on DECL_HAS_DEBUG_EXPR_P.

2018-01-12  Richard Biener  <rguenther@suse.de>

	* lto-streamer-out.c (DFS::DFS_write_tree_body): Process
	DECL_DEBUG_EXPR conditional on DECL_HAS_DEBUG_EXPR_P.
	* tree-streamer-in.c (lto_input_ts_decl_common_tree_pointers):
	Likewise.
	* tree-streamer-out.c (write_ts_decl_common_tree_pointers): Likewise.

From-SVN: r256563