Fix header errors when parsed standalone (#14272)

This is annoying for multiple reasons:

1. LSPs can show many errors for these files.
2. LSP can stop parsing these files completely if there are too many errors,
   resulting in spotty LSP features.

Zend/zend_exceptions.h

@@ -22,6 +22,8 @@
 #ifndef ZEND_EXCEPTIONS_H
 #define ZEND_EXCEPTIONS_H
 
+#include "zend_types.h"
+
 BEGIN_EXTERN_C()
 
 extern ZEND_API zend_class_entry *zend_ce_throwable;