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/change.c b/server/change.c
index 51867dd..5ccdfb8 100644
--- a/server/change.c
+++ b/server/change.c
@@ -73,6 +73,7 @@
     no_satisfied,             /* satisfied */
     no_signal,                /* signal */
     no_get_fd,                /* get_fd */
+    no_close_handle,          /* close_handle */
     change_destroy            /* destroy */
 };