verbatim: reserve enough space for the result also in non-UTF-8 locales

Also when each character is just one byte, parse_verbatim_kbinput()
can produce two bytes; plus the terminating NUL that is three bytes.

This fixes https://savannah.gnu.org/bugs/?58959.

Bug existed since version 4.9, commit 03d296eb.

src/winio.c

@@ -1449,7 +1449,7 @@ int *parse_verbatim_kbinput(WINDOW *win, size_t *count)
  * an escape sequence, and return the resulting number of bytes in count. */
 char *get_verbatim_kbinput(WINDOW *win, size_t *count)
 {
-	char *bytes = charalloc(MAXCHARLEN + 1);
+	char *bytes = charalloc(MAXCHARLEN + 2);
 	int *input;
 
 	/* Turn off flow control characters if necessary so that we can type