MB-9771 Add native incremental index updater

Implementation of native external program for performing
incremental update into the index. The external program receives
necessary info such as index file location, header pos, sorted
operation list files, buffersize, etc via stdin and it efficiently
performs bulk updates to the view btrees and result stats are
sent out via stdout.

Change-Id: Ib35f741e5b615c4dd7f6c3527079538dd56373a0
Reviewed-on: http://review.couchbase.org/31245
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>