[rilmodem] Add support for new RIL API radio tech definition

Map new RADIO_TECH_DC_HSDPA RIL API definition correctly

Signed-off-by: Petri Takalokastari <petri.takalokastari@oss.tieto.com>
[rilmodem] Fix answer and hangup in multiple-call scenarios

Signed-off-by: Martti Piirainen <martti.piirainen@oss.tieto.com>
Merge pull request #74 from ptakalok/master

[rilmodem] Add support for new RIL API radio tech definition
[rilmodem] Listen only network status and core state to set attached state

There is no real equivalent for ofono attached state in RIL interface. So
far attached state has been set based on data registration data. This is
something that cannot be controlled directly by ofono. However ofono core
is implemented on idea that state is controlled by it. Because of that
attached state can be based on data registration state only partially.
This change takes only roaming state from data registration otherwise
attached state is based to core state and network state sent it by
network registration.

Signed-off-by: Jussi Kangas <jussi.kangas@oss.tieto.com>
Merge pull request #76 from marttipiirainen/waiting

[rilmodem] Fix answer and hangup in multiple-call scenarios
Merge pull request #77 from jkangas/master

Request for pulling listening only network and ofono core status to set ofono attached to main branch
gril: prepare set_write_handler for multi-request
gril: provide multi-request support
Merge pull request #78 from jpoutiai/master

provide multi-request support for rilmodem
rilmodem: fixes possible segfault issue in USSD
Merge pull request #79 from jpoutiai/master

rilmodem: fixes possible segfault issue in USSD