server: Return real parent and owner in the create_window request.

Remove computing of parent and owner handles on the client side.
diff --git a/server/protocol.def b/server/protocol.def
index c3ea6a6..9163a36 100644
--- a/server/protocol.def
+++ b/server/protocol.def
@@ -1789,6 +1789,8 @@
     void*          instance;    /* module instance */
 @REPLY
     user_handle_t  handle;      /* created window */
+    user_handle_t  parent;      /* full handle of parent */
+    user_handle_t  owner;       /* full handle of owner */
     int            extra;       /* number of extra bytes */
     void*          class_ptr;   /* pointer to class in client address space */
 @END