Changes made:
 * build script uses /bin/bash instead of /bin/sh
 * Patches the openwrt telnetd to accept a -I interfacename option
   (in openwrt_addons/package/busybox/patches/960-telnetd-bindtodevice.diff)
 * refactored check to see if root PW is set into files/lib/functions/auth.sh
 * files/etc/init.d/telnet now sets the -I eth0 option, and will set the
   IP default TTL to 1 if the root PW isn't set.
 * files/etc/hotplug.d/iface/20-ntpclient will only be run if the root PW has
   been set.
 * prepare - copies openwrt_addons into built_firmware/openwrt/ before
   building;