Remove pri_destroycall() in on_hangup() and
use pri_hangup() instead of the deprecated pri_release().
NOTE: The original patch used PRI_CAUSE_NORMAL_CIRCUIT_CONGESTION for the cause
code, which (without pri_enable_hangup_fix() enabled) emits a RELEASE COMPLETE
message. This version of the patch uses PRI_CAUSE_NORMAL_CLEARING (-1). (stkn)
Additionally, use ftdm_set_state() instead of ftdm_set_state_locked() because the channel
is already locked. (stkn)
Completely-untested-by: Stefan Knoblich <stkn@openisdn.net>
6196a4199e