patch 8.1.0304: 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 set the terminal to raw mode.  This is
            like 8.1.0244 but without the screen redraw and a fix for
            multi-threading suggested by Dominique Pelle.
diff --git a/src/proto/term.pro b/src/proto/term.pro
index c68d7ab..1b8ab5f 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -52,6 +52,7 @@
 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);