Allow for "oldstyle-flush" through php.ini

Change-Id: I0e92e650b5e1c3f58f22047d814262f44eca44a6
Reviewed-on: http://review.couchbase.org/25157
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>