The file targets/$GLUON_TARGET/config becomes optional, as many targets
only used it to set the board and subtarget.

Also fix targets without subtarget.

This default to n now by default

These packages are included by OpenWrt by default on this target and don't
need to be specified manually.

gluon-neighbour-info: Support sub-second timeout

This was broken due to the switch to Chaos Calmer.

This fixes MAC address conflicts on devices which use the eth0 as primary
address.

This should fix the signal strength indicators on the TP-Link CPE210/510.

These targets don't have a WLAN adapter by default, so it doesn't make
sense to default to the phy0 address.

Original patch by @MPW1412

Fixes build for brcm2708 targets

It seems to have been deleted accidentially.

Do not use error() in gluon-neighbour-info

error() is a glibc specific function and should not be used in
code meant to be portable.

Tested-by: @RubenKelevra

gluon-status-page: API

This limits the number of concurrent users to 2 or 3 (approx. 4 connections per
user), greatly reducing DoS potential.

The TL-WR741ND will identify itself as a TL-WR740N/ND as well. This is fine as
the images are identical anyways.

Recent changes in the routing configuration of OpenWrt broke source address
selection, sometimes leading to the node trying to contact other addresses in
the mesh network from the next-node address.

Revert the problematic commits until this has been solved upstream.

The oldpackages repo has been dropped for Chaos Calmer.

gluon-announce, ...: don't output empty lists where not appropriate