Add {DLT,LINKTYPE}_BLUETOOTH_LINUX_MONITOR for BlueZ.

This is a new link-layer header type for the Bluetooth Linux Monitor in
the BlueZ Bluetooth stack.
Add new Bluetooth link-layer header types.
Add support for Bluetooth Linux Monitor interface

Interface "bluetooth_monitor" is used to monitoring all Bluetooth
adapters together on Linux platform.
Merge pull request #342 from MichalLabedzki/master

Add support for Bluetooth Linux Monitor interface
Check for HCI_CHANNEL_MONITOR for Linux Bluetooth Monitor support.

Support the Linux Bluetooth Monitor mechanism if:

	we support Linux Bluetooth;

	struct sockaddr_hci includes an hci_channel field;

	HCI_CHANNEL_MONITOR is defined by the Bluetooth headers;

as there are some 3.x kernel versions in which struct sockaddr_hci
includes an hci_channel field but in which HCI_CHANNEL_MONITOR is not
defined.