Addition of postfix_flags variable to rc.subr startup script.
This variable is passed to postfix-script on startup, allowing
administrators to do things like postfix_flags="-c /my/place/postfix"
(alternate location of main.cf and master.cf), or postfix_flags="-v"
(for verbose logging). See postfix(1) manpage for flags.
Reviewed by: Vivek Khera <firstname.lastname@example.org>
Approved by: philip