faster banners, on FIN instead of TCB destruction

src/main-conf.c

src/masscan-app.h

src/proto-banner1.c

src/proto-banner1.h

src/proto-banout.c

src/proto-tcp.c

src/ranges.c

src/rawsock-getif.c

src/rawsock-getroute.c

src/rawsock-pcapfile.c