txtinfo: only listen on IPv6 when running under IPv6
txtinfo: only listen on IPv6 when running under IPv6

When the IPV6_V6ONLY flag is not set then olsrd running on IPv6
will listen on both IPv6 and IPv4 ports. A subsequent process
running on IPv4 can't listen on the same IPv4 port.

Signed-off-by: Patrick Grimm <cbb7353e6d953ef360baf960c122346276c6e320@lunatiki.de>

diogomg/olsrd,diogomg/olsrd-binary-heap,sebkur/olsrd,diogomg/olsrd-binary-heap,sebkur/olsrd,diogomg/olsrd-binary-heap,sebkur/olsrd,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap,sebkur/olsrd,diogomg/olsrd,cholin/olsrd,cholin/olsrd,cholin/olsrd,diogomg/olsrd,diogomg/olsrd,sebkur/olsrd,diogomg/olsrd,cholin/olsrd,diogomg/olsrd,cholin/olsrd,diogomg/olsrd,sebkur/olsrd,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap