CCBC-248 Do not disable config.h on UNIX-like platforms

Change-Id: Ie2b4c9af600846e220afd781b75a8073bc6582aa
Reviewed-on: http://review.couchbase.org/28404
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>