xapian-bridge C port

endlessm/eos-sdk#2463
Actually I'd prefer not to. I've noticed in the past that Automake has no reservations whatsoever about breaking undocumented variables like this.

I'd like to use this if possible, though, so I've asked about it on Stack Overflow [here](http://stackoverflow.com/questions/26980634/is-dc-install-base-a-supported-feature) and we could also ask the Automake mailing list.