patch 8.1.0244: no redraw when using a STOP signal on Vim and then CONT

Problem:    No redraw when using a STOP signal on Vim and then a CONT signal.
Solution:   Catch the CONT signal and force a redraw. (closes #3285)
diff --git a/src/proto/term.pro b/src/proto/term.pro
index 7eafdef..9a9606b 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -50,6 +50,7 @@
 int mouse_has(int c);
 int mouse_model_popup(void);
 void scroll_start(void);
+void cursor_on_force(void);
 void cursor_on(void);
 void cursor_off(void);
 void term_cursor_mode(int forced);