* ipa-reference.c (check_call): Noreturn notrhow calls do not write
	to memory.
	(analyze_function): When analyzing noreturn nothrow call, do not compute
	written stats; free bitmaps of vars early if possible.
	(generate_summary): Only update bitmaps if computed.
	(propagate): Only dump bitmaps if computed.
	(ipa_reference_read_summary): Fix pasto.

From-SVN: r153529