emulator: Register card when establish SLC
hfp_ag_bluez5: Create card for emulator when connect
emulator: Set local and remote address of card
hfp_ag_bluez5: Pass fd to card creation

We can extract local and remote address from the file descriptor.
emulator: Add init and cleanup functions
main: Call emulator init and cleanup functions
hfp: Transfer HFP version definitions to hfp.h

When these definitions were located in slc.h and you want to uset them,
you must include gatchat.h.

Now you only need to include hfp.h.
phonesim: Include hfp.h
hfp_ag_bluez5: Include hfp.h
emulator: Add a Card driver for HFP 1.6

This is just the skeleton of a Handsfree Audio Card for the AG side of
HFP 1.6.
emulator: Set card version
hfp_ag_bluez5: Pass version to card creation
hfp_ag_bluez5: Register HFP AG version 1.6
emulator: Add Codec Negotiation feature

This commits adds Codec Negotiation to the emulator's list of features.
emulator: Add AT+BAC support

When the emulator receives a AT+BAC SET command, it stores the
available HF codecs.
emulator: Keep information about AT+BAC calls

The AG must only init the codec negociation procedure if the HF has
already sent an AT+BAC command in the current Service Level Connection.
emulator: Respond to AT+BCC command

This commit verifies the conditions where the AT+BCC command will fail.

The codec connection setup is missing.
include: Add g_at_server_register_response()
gatserver: Implement g_at_server_register_response

Certain AT commands only make sense if received in response to another
AT command, and this is especially important when sending unsolicited
commands that receives responses. But there is no mechanism on
gatserver side that allows to implement this behavior.

This commit adds a function which indicates what AT command the
gatserver is expecting. If the next command is not the desired one,
then a ERROR command is sent.
emulator: Send unsolicited +BCS

This commit sends a unsolicited +BCS command with the selected codec
when the AG receives with success an +BCC command.

Currently the codec is hardcoded to CVSD.