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.

src/proto/os_amiga.pro

@@ -31,7 +31,7 @@ int mch_can_exe(char_u *name, char_u **path, int use_path);
 int mch_nodetype(char_u *name);
 void mch_early_init(void);
 void mch_exit(int r);
-void mch_settmode(int tmode);
+void mch_settmode(tmode_T tmode);
 int mch_get_shellsize(void);
 void mch_set_shellsize(void);
 void mch_new_shellsize(void);

src/proto/os_mswin.pro

@@ -10,7 +10,7 @@ int mch_FullName(char_u *fname, char_u *buf, int len, int force);
 int mch_isFullName(char_u *fname);
 void slash_adjust(char_u *p);
 int vim_stat(const char *name, stat_T *stp);
-void mch_settmode(int tmode);
+void mch_settmode(tmode_T tmode);
 int mch_get_shellsize(void);
 void mch_set_shellsize(void);
 void mch_new_shellsize(void);

src/proto/os_unix.pro

@@ -48,7 +48,7 @@ int mch_nodetype(char_u *name);
 void mch_early_init(void);
 void mch_free_mem(void);
 void mch_exit(int r);
-void mch_settmode(int tmode);
+void mch_settmode(tmode_T tmode);
 void get_stty(void);
 int get_tty_info(int fd, ttyinfo_T *info);
 void mch_setmouse(int on);

src/proto/os_vms.pro

@@ -1,5 +1,5 @@
 /* os_vms.c */
-void mch_settmode(int tmode);
+void mch_settmode(tmode_T tmode);
 int mch_get_shellsize(void);
 void mch_set_shellsize(void);
 char_u *mch_getenv(char_u *lognam);

src/proto/os_win32.pro

@@ -39,7 +39,7 @@ int mch_nodetype(char_u *name);
 vim_acl_T mch_get_acl(char_u *fname);
 void mch_set_acl(char_u *fname, vim_acl_T acl);
 void mch_free_acl(vim_acl_T acl);
-void mch_settmode(int tmode);
+void mch_settmode(tmode_T tmode);
 int mch_get_shellsize(void);
 void mch_set_shellsize(void);
 void mch_new_shellsize(void);