Merge changes from topic 'system-bt'

* changes:
  Change path to bluetooth stack
  Include new hci_audio.h for SCO_* constants
  Move gen-buildcfg.sh into libbt so there isn't project cross-reference
tree: 076dd664ae6c23149f80860b0e201d58d069d07e
  1. conf/
  2. include/
  3. src/
  4. Android.mk
  5. gen-buildcfg.sh
  6. vnd_buildcfg.mk