Move autotools related files to config subdirectory

Change-Id: Ia70a4ee754f03d871530b3fb86ce3ec5e1f4a7a8
Reviewed-on: http://review.couchbase.org/43692
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>