patch 8.2.2754: :sleep! does not always hide the cursor

Problem:    :sleep! does not always hide the cursor.
Solution:   Add the cursor_is_asleep flag. (Jeremy Lerner, closes #8097,
            closes #7998)
diff --git a/src/proto/term.pro b/src/proto/term.pro
index 1b37802..efb2555 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -56,6 +56,9 @@
 void cursor_on_force(void);
 void cursor_on(void);
 void cursor_off(void);
+int cursor_is_sleeping(void);
+void cursor_sleep(void);
+void cursor_unsleep(void);
 void term_cursor_mode(int forced);
 void term_cursor_color(char_u *color);
 int blink_state_is_inverted(void);