Remove dead code and replace numeric bitpool values by macro definitions.
Maximal bitpool value in fill_capabilities() was reduced from 64 to 53
(SBC_BITPOOL_HQ_JOINT_STEREO_44100) because default_bitpool() already set
maximal value to 53.
This patch does not change SBC behavior as maximal bitpool was already
limited to 53. So it is just clean up.
This patch introduce new modular API for bluetooth A2DP codecs. Its
benefits are:
* bluez5-util and module-bluez5-device does not contain any codec specific
code, they are codec independent.
* For adding new A2DP codec it is needed just to adjust one table in
a2dp-codec-util.c file. All codec specific functions are in separate
codec file.
* Support for backchannel (microphone voice). Some A2DP codecs (like
FastStream or aptX Low Latency) are bi-directional and can be used for
both music playback and audio call.
* Support for more configurations per codec. This allows to implement low
quality mode of some codec together with high quality.
Current SBC codec implementation was moved from bluez5-util and
module-bluez5-device to its own file and converted to this new A2DP API.
