user: Fix WM_QUIT message ordering from PostQuitMessage.
Added a new server call as PostQuitMessage should set a flag in the
message queue to return the WM_QUIT message when there are no other
pending messages, rather than posting a message to the thread queue as
it does at the moment.
diff --git a/server/request.h b/server/request.h
index 1fecb0f..91b314f 100644
--- a/server/request.h
+++ b/server/request.h
@@ -232,6 +232,7 @@
 DECL_HANDLER(get_queue_status);
 DECL_HANDLER(wait_input_idle);
 DECL_HANDLER(send_message);
+DECL_HANDLER(post_quit_message);
 DECL_HANDLER(get_message);
 DECL_HANDLER(reply_message);
 DECL_HANDLER(accept_hardware_message);
@@ -449,6 +450,7 @@
     (req_handler)req_get_queue_status,
     (req_handler)req_wait_input_idle,
     (req_handler)req_send_message,
+    (req_handler)req_post_quit_message,
     (req_handler)req_get_message,
     (req_handler)req_reply_message,
     (req_handler)req_accept_hardware_message,