As BlueZ 5 introduced backwards incompatible API changes, and we want to
keep support for BlueZ 4 based plugins for some time, we need to separate
the plugins that are based on BlueZ 4 from the ones based on BlueZ 5.
The bluetooth.c plugin has now been renamed to bluez4.c and the hfp_hf.c
plugin is renamed to hfp_hf_bluez4. This will make it easy to add a
HFP HF plugin for BlueZ 5.
By default, both stderr and syslog messages go to the systemd journal,
which results in duplicate messages being logged.
Thanks to Vinicius Costa Gomes for pointing out this problem.
If the ATD*99# dial fails for some reason, NO CARRIER, for example, we
need to disconnect the bluetooth link and do further clean up on
disconnect_callback().
If we do not shut it down the fd can remain opened. This make impossible
to try a re-connect: busy is returned in this case.
We call shutdown here to make sure that the link is always closed.