main/php.h: add #include directives that some extensions rely on

These are currently indirectly included, but in order to retain
source compatibility with out-of-tree extensions when #includes are
cleaned up in those parts of PHP, we need to re-add them to the
"php.h" header.

Author: MaxKellermann

main/php.h

@@ -434,4 +434,18 @@ END_EXTERN_C()
 
 #include "php_reentrancy.h"
 
+/* the following headers used to be included indirectly, and we have
+ * them here only for backwards compatibility with thirdparty
+ * extensions */
+#include "php_globals.h"
+#include "php_ini.h"
+#include "zend_arena.h"
+#include "zend_iterators.h"
+#include "zend_multiply.h"
+#include "zend_objects.h"
+#include "zend_strtod.h"
+#include <errno.h>
+#include <float.h>
+#include <string.h>
+
 #endif