Added prototype Response System library port from the Alien Swarm SDK

sp/src/game/server/ai_baseactor.cpp

@@ -2033,7 +2033,11 @@ bool CAI_BaseActor::UseSemaphore( void )
 
 CAI_Expresser *CAI_BaseActor::CreateExpresser()
 {
+#ifdef NEW_RESPONSE_SYSTEM
+	m_pExpresser = new CAI_ExpresserWithFollowup(this);
+#else
 	m_pExpresser = new CAI_Expresser(this);
+#endif
 	return m_pExpresser;
 }