Bug 1031185: Wrap Bluedroid interfaces in classes (under bluedroid2/), r=btian

This patch adds classes around all Bluedroid interfaces that are
currently used by Gecko. These are Core, Socket, Handsfree, A2DP,
and AVRCP.

All arguments and return values are still Bluedroid types and
constants. Future patches will convert them to interface-neutral
artifacts.
Bug 1031185: Convert Bluetooth to use Bluedroid wrappers (under bluedroid2/), r=btian

This patch converts the Bluedroid backend to use the wrapper
classes. The affected interfaces are Core, Sockets, Handsfree,
A2DP, and AVRCP.