- Remove unused NAS_config(): It does most of what the highly similar
  nas_config() does.
- Remove unused set_gateway()
- Remove unused blocking_NAS_config()
- Remove unused functions getNetMask()
- Remove unused broadcast functionality: functions setBroadcastAddress()
  and getBroadcastAddress(), as well as global variable broadcastAddr
  are not used in consumers. Remove it.
- Make functions static