Remove old ARG_COUNT() macro

Use ZEND_NUM_ARGS() instead.

Clsoes phpGH-5551

Author: Girgias

UPGRADING.INTERNALS

@@ -16,6 +16,7 @@ PHP 8.0 INTERNALS UPGRADE NOTES
   m. All internal functions must have arginfo
   n. zend_hash_sort compare function signature change
   o. cast_object() object handler is now required
+  p. ARG_COUNT() macro removed
 
 2. Build system changes
   a. Abstract
@@ -114,6 +115,8 @@ PHP 8.0 INTERNALS UPGRADE NOTES
   o. The cast_object() handler is now required, i.e. must be non-null. You can
      indicate that casting is not supported by always returning FAILURE.
 
+  p. The ARG_COUNT() macro has been removed use ZEND_NUM_ARGS() instead.
+
 ========================
 2. Build system changes
 ========================

Zend/zend_API.h

@@ -408,7 +408,6 @@ ZEND_API const char *zend_get_type_by_const(int type);
 
 #define WRONG_PARAM_COUNT					ZEND_WRONG_PARAM_COUNT()
 #define WRONG_PARAM_COUNT_WITH_RETVAL(ret)	ZEND_WRONG_PARAM_COUNT_WITH_RETVAL(ret)
-#define ARG_COUNT(dummy)					EX_NUM_ARGS()
 #define ZEND_NUM_ARGS()						EX_NUM_ARGS()
 #define ZEND_WRONG_PARAM_COUNT()					{ zend_wrong_param_count(); return; }
 #define ZEND_WRONG_PARAM_COUNT_WITH_RETVAL(ret)		{ zend_wrong_param_count(); return ret; }