Add 'abicheck' metadata

This files will help determine ABI compatibility in the future.

Change-Id: Ifd0c9a58ae44c7878d9c7274afeeca39d9aeb726
Reviewed-on: http://review.couchbase.org/38464
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>