Fix dtest to build properly with extensions.

 Fix dtest to build properly with extensions.

 Modify dat.h dat_event to include event_extension_data[8].
 Extend struct dat_event outside of extension build
 switch to enable non-extended applications to work
 with extended libraries. Otherwise, there is a potential
 for the event callee to write back too much event data
 and exceed callers non-extended event buffer.

 Signed-off by: Arlin Davis <ardavis@ichips.intel.com>