[packages] mdnsresponder: fix compile

Fix for bison-3 syntax.
adapt patch from Jonathan Perkin (jperkin)
http://ftp.netbsd.org/pub/pkgsrc/current/pkgsrc/net/mDNSResponder/patches/patch-mDNSShared_dnsextd__parser.y

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>