Include platform.h insteadof windows.h

Change-Id: I886789eb78119f77b9559b35508e82aec383cfd9
Reviewed-on: http://review.couchbase.org/30387
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>