Adding Bluetooth communication is desirable for all sigrok supported
platforms. The BlueZ library is available on Linux which will receive
support first. Check for the BlueZ library's presence, determine a
HAVE_BLUETOOTH summary state, and extend the HAVE_SERIAL_COMM check.
Print version details for the external library.
This commit extends build support and version information, but does not
yet include the implementation of the serial transport primitives.