relax format assertions for fstat() results on Windows

According to https://www.php.net/manual/en/function.stat.php the serial
number of the volume that contains the file is returned for the "dev" entry
as a 64-bit unsigned integer which may overflow.

Tests/Caster/SplCasterTest.php

@@ -104,7 +104,7 @@ public function testCastFileObject()
   flags: DROP_NEW_LINE|SKIP_EMPTY
   maxLineLen: 0
   fstat: array:26 [
-    "dev" => %d
+    "dev" => %i
     "ino" => %i
     "nlink" => %d
     "rdev" => 0