Bug 944299 - 1/6: initial import of libbt from AOSP

See https://android.googlesource.com/platform/hardware/broadcom/libbt/+/android-4.3_r2.1
Bug 944299 - 2/6: remove non-goldfish bits
Bug 944299 - 3/6: automatically detect userial port.
Bug 944299 - 4/6: add bdroid_buildcfg.h.
Bug 944299 - 5/6: add bt_config.xml.
Bug 944299 - 6/6: Skip bluetooth chipset HW configuration

We don't need to support HW baud rate and download patchram for QEMU
Bluetooth HCI emulation module, skip HW configuration procedures.