The "should we encode" check was split off from add_rfc2047() into its
own function in 41dd00bad3 (format-patch: fix rfc2047 address encoding
with respect to rfc822 specials, 2012-10-18). But only the "add" half
needs to know the rfc2047_type, since it only affects _how_ we encode,
not whether we do.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>