fix anchor rules with filter opts, introduce filteropts_to_rule()

fix anchor rules with filter opts, introduce filteropts_to_rule()

Some filter options were parsed but not set on anchor rules due to missing
copies of the respective struct members:

	$ cat pf.conf
	queue rq on trunk0 bandwidth 1G
	queue dq parent rq bandwidth 1G default
	anchor a set queue dq
	$ pfctl -vnf pf.conf | fgrep queue
	anchor "a" all

Fix this by moving common code from `anchorrule' and `pfrule' into a new
helper filteropts_to_rule().

Input from henning and benno
OK henning sashan jca