Mark PDO::setAttribute() $value as mixed

For consistency with PDOStatement::setAttribute(). Attribute values
can for example also be bool.

This is backwards-compatible, as mixed is the same as no type for
parameter variance.

ext/pdo/pdo_dbh.stub.php

@@ -45,9 +45,6 @@ public function quote(string $string, int $type = PDO::PARAM_STR) {}
     /** @return bool */
     public function rollBack() {}
 
-    /**
-     * @param array|int $value
-     * @return bool
-     */
-    public function setAttribute(int $attribute, $value) {}
+    /** @return bool */
+    public function setAttribute(int $attribute, mixed $value) {}
 }

ext/pdo/pdo_dbh_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 788d1cd616c140df4072c6e0564c2995fbdc84ad */
+ * Stub hash: 2952abcfab855d46f6e5fb9dcf447d87f06b6881 */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_PDO___construct, 0, 0, 1)
 	ZEND_ARG_TYPE_INFO(0, dsn, IS_STRING, 0)
@@ -53,7 +53,7 @@ ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_PDO_setAttribute, 0, 0, 2)
 	ZEND_ARG_TYPE_INFO(0, attribute, IS_LONG, 0)
-	ZEND_ARG_INFO(0, value)
+	ZEND_ARG_TYPE_INFO(0, value, IS_MIXED, 0)
 ZEND_END_ARG_INFO()