xapian-bridge C port

endlessm/eos-sdk#2463
Good question; not sure if it's a "stable" API we can rely on, but I took this from  udisks: http://cgit.freedesktop.org/udisks/tree/Makefile.am#n13.
Other daemons seem to do the same, e.g. upower: http://cgit.freedesktop.org/upower/tree/Makefile.am#n55

So, as long as other "important" projects upstream do this, I think we can keep it too. I can open a backlog issue for the metrics event recorder if you agree.