Point default feeds to marcet.info's mirrors

Signed-off-by: Javier Marcet <javier@marcet.info>
WNDR3700-barrier-r42956-2014-10-18-2337-openwrt.patch from https://forum.openwrt.org/viewtopic.php?id=28392

Signed-off-by: Javier Marcet <javier@marcet.info>
openssl: link zlib

Signed-off-by: Javier Marcet <javier@marcet.info>
dropbear: only listen on ipv4

Signed-off-by: Javier Marcet <javier@marcet.info>