Revert "Fix bug GH-1 (mysqli_sql_exception->sqlstate is inaccessible)"

This reverts commit 64fca5c.

Author: kamil-tekiela

ext/mysqli/mysqli.c

@@ -568,7 +568,7 @@ PHP_MINIT_FUNCTION(mysqli)
 	mysqli_exception_class_entry = zend_register_internal_class_ex(&cex, spl_ce_RuntimeException);
 	mysqli_exception_class_entry->ce_flags |= ZEND_ACC_FINAL;
 	zend_declare_property_long(mysqli_exception_class_entry, "code", sizeof("code")-1, 0, ZEND_ACC_PROTECTED);
-	zend_declare_property_string(mysqli_exception_class_entry, "sqlstate", sizeof("sqlstate")-1, "00000", ZEND_ACC_PUBLIC);
+	zend_declare_property_string(mysqli_exception_class_entry, "sqlstate", sizeof("sqlstate")-1, "00000", ZEND_ACC_PROTECTED);
 
 	REGISTER_MYSQLI_CLASS_ENTRY("mysqli_driver", mysqli_driver_class_entry, class_mysqli_driver_methods);
 	ce = mysqli_driver_class_entry;