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/term.c b/src/term.c
index 97ddf8b..cede4b8 100644
--- a/src/term.c
+++ b/src/term.c
@@ -3834,16 +3834,23 @@
 static int cursor_is_off = FALSE;
 
 /*
- * Enable the cursor.
+ * Enable the cursor without checking if it's already enabled.
+ */
+    void
+cursor_on_force(void)
+{
+    out_str(T_VE);
+    cursor_is_off = FALSE;
+}
+
+/*
+ * Enable the cursor if it's currently off.
  */
     void
 cursor_on(void)
 {
     if (cursor_is_off)
-    {
-	out_str(T_VE);
-	cursor_is_off = FALSE;
-    }
+	cursor_on_force();
 }
 
 /*