Fix the #include order for config.h.
Add #include "config.h" directives where needed.

diff --git a/windows/class.c b/windows/class.c
index e0bacb0..80c03db 100644
--- a/windows/class.c
+++ b/windows/class.c
@@ -12,6 +12,7 @@
  *   classes are getting registered with wrong hInstance.
  */
 
+#include "config.h"
 #include "wine/port.h"
 
 #include <stdlib.h>