WLAN-SI are running into the limit.  Cool.

- We keep the "export-table" option for compatibility reasons.

- It overrides the selection of source-specific tables.  Not sure if it
  is the right thing to do.

Thanks to Jernej Kos <jernej@kos.mx> for its review.

The previous patch to only write sysctls when needed failed to restore
values that was 0 before being set by babeld. This fixes that.
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

This adds a configuration flag to skip kernel (sysctl) setup on daemon
startup. This can be useful if running in, e.g., a container environment
where setting sysctls are not allowed.
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

This reworks the sysctl handling to only write a sysctl if it is not
already the desired value. In addition, the Linux sysctl knobs are now
stored in a lookup table which is looped through, to avoid code
duplication in the setup routine.
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

There is no equivalent config-file option, since I'm worried about config
files being copied between nodes.

This patch fix the non-disambiguation behaviour: we were looking to
disambiguation entries to remove or replace, which is a complete non-sense,
since there should not being disambiguation entries.

Sigh.

This is simpler and avoids issues with changing router-ids.

This increases the chances for a stable router-id in case the set of
interfaces changes.