__init has a naming collision with C++ and prevents ubus_common.h
from being included. Instead, use __constructor as defined from
libubox.
Signed-off-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
this is mainly useful to have a single location to read the setting
from, when it is used multiple times at build time (which it will in a
following patch) :)
