Zend/Optimizer/optimize_temp_vars_5: add missing include

Author: MaxKellermann

Zend/Optimizer/optimize_temp_vars_5.c

@@ -21,6 +21,7 @@
 
 #include "Optimizer/zend_optimizer.h"
 #include "Optimizer/zend_optimizer_internal.h"
+#include "zend_arena.h"
 #include "zend_API.h"
 #include "zend_constants.h"
 #include "zend_execute.h"