Bug 1064264: Add AVRCP_UID_SIZE to Bluetooth (under bluetooth2/), r=btian

The constant AVRCP_UID_SIZE replaces the corresponding Bluedroid
constant BTRC_UID_SIZE.
Bug 1064264: Fix constants in Bluedroid HFP manager (under bluetooth2/), r=btian

This patch replaces the remaining Bluedroid constants from Bluedroid's
|BluetoothHfpManager| with Gecko constants.
Bug 1064264: Make Bluetooth AVRCP interface generally available (under bluetooth2/), r=btian

The methods of |BluetoothAVRCPInterface| are now always available. On
Android versions before 18, which don't support AVRCP, they always
fail with STATUS_UNSUPPORTED.
Bug 1064264: Cleanup ANDROID_VERSION from BluetoothA2DPManager (under bluetooth2/), r=btian

All interfaces for Bluetooth profiles are now always available, so we
don't have to check for specific versions of Bluedroid. Instead, we
try to call the methods, and check their results.
Bug 1064264: Remove references to Android from BluetoothServiceBluedroid, r=btian