This patch fixes problem for modems that cannot terminate
DIALING/ALERTING calls with CHUP=1X. The main change is that
voicecall driver's hangup function is split into the functions
hangup_all and hangup_active.
Changes:
- In cases where hangup previously was used, hangup_all is used
if implemented otherwise hangup_active is used.
- Call in state DIALING/ALERTING is released with hangup_active if
implemented.
- manager_hangup_all will simply call hangup_all if implemented.
- manager_hangup_all will release calls in state
ALERTING/DIALING/INCOMING using hangup_active otherwise
release_specific.