Add sanopt for ASAN_MARK poison and unpoison.

	* sanopt.c (sanopt_optimize_walker): Set contains_asan_mark.
	(sanopt_optimize): Add new argument.
	(sanitize_asan_mark_unpoison): New function.
	(maybe_contains_asan_check): Likewise.
	(sanitize_asan_mark_poison): Likewise.
	(pass_sanopt::execute): Call the new functions.

From-SVN: r243611