Fix mingw build

Change-Id: Ib75c467c0c003c42d83ef06005fab5fa0421ca26
Reviewed-on: http://review.couchbase.org/40945
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>