Support Bluetooth on Mac OS X

hello,
Currently the Mac OS X Bluetooth support uses obsolete APIs that do not 
work on the latest versions of Mac OS X. Therefore that support just 
does not compile.

This patch reintroduces Bluetooth support on Mac OS X, using the most 
recent API. I only tested it on El Capitan. It applies to latest Git 
master.

It is written in Objective C yet it compiles and links smoothly with the 
rest of the program.

I uploaded it to Savannah, at https://savannah.nongnu.org/patch/?8891

Regards,
Fabrizio