Make ABI compliance checking a bit nicer

Change-Id: I71dba03db5d7a07f1af636763cf7043579e02e65
Reviewed-on: http://review.couchbase.org/43050
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>