patch 9.1.0344: Cursor wrong after using setcellwidth() in terminal

Problem:  Cursor wrong after using setcellwidth() in terminal
          (mikoto2000)
Solution: output additional spaces, so the behaviour matches the GUI
          (mikoto2000)

fixes: #14539
closes: #14540

Signed-off-by: mikoto2000 <mikoto2000@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
Fix CUI `setcellwidths` characters draw behavior to same GUI behavior.

src/mbyte.c

@@ -5542,6 +5542,20 @@ string_convert_ext(
     return retval;
 }
 
+/*
+ * Return 1 or 2 when "c" is in the cellwidth table.
+ * Return 0 if not.
+ */
+    int
+get_cellwidth(int c UNUSED)
+{
+#ifdef FEAT_EVAL
+    return cw_value(c);
+#else
+    return 0;
+#endif
+}
+
 #if defined(FEAT_EVAL) || defined(PROTO)
 
 /*