bug#9771: 24.0.90; Redisplay problems with control characters

[Eli Zaretskii <eliz@gnu.org>]

> From: Johan Bockgård <bojohan@gnu.org>
> Date: Mon, 17 Oct 2011 00:24:30 +0200
> 
> 1. Abort in move_it_by_lines (with bidi)
> 
> emacs -Q
> C-u 2000 C-q 0 RET
> M-<
> M->
> 
> Fatal error (6)Aborted (core dumped)
> 
> (gdb) bt
> #0  abort () at emacs.c:385
> #1  0x0000000000451a48 in move_it_by_lines (it=0x7fffffffc620, dvpos=0)
>     at xdisp.c:8907
> #2  0x00000000004c0717 in Frecenter (arg=10) at window.c:5107
> #3  0x000000000060ce90 in Ffuncall (nargs=<optimized out>, args=0x7fffffffd460)
>     at eval.c:2974
> [...]
> 
> The following assertion fails:
> 
>   [move_it_by_lines]
> 
>     if (dvpos == 0)
>       {
>         /* DVPOS == 0 means move to the start of the screen line.  */
>         move_it_vertically_backward (it, 0);
>         xassert (it->current_x == 0 && it->hpos == 0);
> 
> (gdb) p it->current_x
> $1 = 10
> (gdb) p it->hpos
> $2 = 1

This part should be fixed in revision 106106 on the trunk.