Fix event test for win32
Fix event test for win32

Newer libevents defines EVENT__ and not _EVENT.
This is a temporary fix until we upgrade the dependency to
libevent2 for all platforms.

Change-Id: I868dfbec8c0f37c9f2580211d114a3f1b6c761a8
Reviewed-on: http://review.couchbase.org/34774
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>
Tested-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

mrkwse/memcached,couchbase/memcached,daverigby/kv_engine,jimwwalker/memcached,cloudrain21/memcached-1,daverigby/memcached,daverigby/memcached,owendCB/memcached,daverigby/memcached,daverigby/kv_engine,daverigby/kv_engine,cloudrain21/memcached-1,jimwwalker/memcached,owendCB/memcached,owendCB/memcached,cloudrain21/memcached-1,couchbase/memcached,couchbase/memcached,jimwwalker/memcached,owendCB/memcached,daverigby/memcached,daverigby/kv_engine,mrkwse/memcached,mrkwse/memcached,couchbase/memcached,mrkwse/memcached,cloudrain21/memcached-1