Added a close_handle method to the object operations, and use it to
implement registry notifications and the strange behavior of
CloseHandle on winstation/desktop handles.

diff --git a/server/request.c b/server/request.c
index aa5c09d..4a2c80a 100644
--- a/server/request.c
+++ b/server/request.c
@@ -95,6 +95,7 @@
     NULL,                          /* satisfied */
     no_signal,                     /* signal */
     no_get_fd,                     /* get_fd */
+    no_close_handle,               /* close_handle */
     master_socket_destroy          /* destroy */
 };