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/hook.c b/server/hook.c
index 125f346..c3a0244 100644
--- a/server/hook.c
+++ b/server/hook.c
@@ -79,6 +79,7 @@
     NULL,                         /* satisfied */
     no_signal,                    /* signal */
     no_get_fd,                    /* get_fd */
+    no_close_handle,              /* close_handle */
     hook_table_destroy            /* destroy */
 };