Include strings.h to get strcasecmp

Change-Id: I627c92fc356fb71fa07e3b91c499fc2d9cd7f911
Reviewed-on: http://review.couchbase.org/35053
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>