Added music on hold for incoming GSM call.
Adaptive jitter buffer is introduced.
Faster registration and re-registration.
Added incoming feature in the dialer (only if the operator code is enabled with incoming option). "Do not disturb" option is also added if the user doesn't want to be notified for incoming calls.
Added option to choose between Low Bandwidth (6 kbps) and Normal Bandwidth modes.
Fixed some issues including ring tone for outgoing calls.