* cfgexpand.c (struct stack_vars_data): Add asan_base and asan_alignb
	fields.
	(expand_stack_vars): For -fsanitize=address, use (and set initially)
	data->asan_base as base for vars and update asan_alignb.
	(expand_used_vars): Initialize data.asan_base and data.asan_alignb.
	Pass them to asan_emit_stack_protection.
	* asan.c (asan_detect_stack_use_after_return): New variable.
	(asan_emit_stack_protection): Add pbase and alignb arguments.
	Implement use after return sanitization.
	* asan.h (asan_emit_stack_protection): Adjust prototype.
	(ASAN_STACK_MAGIC_USE_AFTER_RET, ASAN_STACK_RETIRED_MAGIC): Define.

From-SVN: r205476