patch 8.2.0774: t_TI and t_TE are output when using 'visualbell'

Problem:    t_TI and t_TE are output when using 'visualbell'. (Dominique
            Pelle)
Solution:   Do not change the terminal mode for a short sleep.  Do not output
            t_TI and t_TE when switching to/from TMODE_SLEEP. Make tmode an
            enum.
diff --git a/src/os_mswin.c b/src/os_mswin.c
index 1c987c2..8000953 100644
--- a/src/os_mswin.c
+++ b/src/os_mswin.c
@@ -553,7 +553,7 @@
 
 #if (defined(FEAT_GUI_MSWIN) && !defined(VIMDLL)) || defined(PROTO)
     void
-mch_settmode(int tmode UNUSED)
+mch_settmode(tmode_T tmode UNUSED)
 {
     // nothing to do
 }