bluetooth: Lock down creation of AF_BLUETOOTH sockets.

Only root or processes with gid AID_NET_BT or AID_NET_BT_ADMIN
can create RFCOMM, SCO and L2CAP sockets.

Only root or process with gid AID_NET_BT_ADMIN can open other
AF_BLUETOOTH sockets (for example HCI).

This required introducing android_aid.h with the hardcoded
android id's.

Signed-off-by: Brian Swetland <swetland@google.com>