Zend/Optimizer/compact_literals: add missing include

Author: MaxKellermann

Zend/Optimizer/compact_literals.c

@@ -23,6 +23,7 @@
 
 #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"