Bug 1103872: Add helpers for Bluetooth daemon Handsfree support (under bluetooth2/), r=btian

This patch adds helpers for packing, unpacking and converting
Handsfree values to and from Bluetooth PDUs.
Bug 1103872: Add Handsfree module for Bluetooth daemon (under bluetooth2/), r=btian
Bug 1103872: Add Handsfree interface for Bluetooth daemon (under bluetooth2/), r=btian
Bug 1103872: Support Handsfree profile when using Bluetooth daemon (under bluetooth2/), r=btian