MB-30253 - regexp.dfaBuilder reuses prealloced insts array
MB-30253 - regexp.dfaBuilder reuses prealloced insts array

From a bleve-query microbenchmark on 50K doc wikipedia dataset, using
a regexp query-string for a high-frequency term, like "text:stephen*",
throughput went from 790 q/sec to 870 q/sec after the change.

Change-Id: I7dd758ab4b5e87b58358972719f4c6526a4bcd2e
Reviewed-on: http://review.couchbase.org/96088
Well-Formed: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Marty Schoch <ba9951d7d66412e2a57aea395f01176a793cf5eb@gmail.com>
Tested-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>

couchbase/vellum