display bug for empty lines in recent git snapshot

[Giorgos Keramidas <keramida@ceid.upatras.gr>]

I've compiled a new snapshot of Emacs after a few weeks from the git
mirror at git://repo.or.cz/emacs.git and noticed that there's now a
display bug with empty lines.

The latest snapshot I compiled was last afternoon, from:

    commit 30286b8e4b37619c8d6bf5bc01840606f26d9cf7
    Author: Adrian Robert <Adrian.B.Robert@gmail.com>
    Date:   Tue Oct 26 16:20:00 2010 +0300

        * term/ns-win.el (ns-new-frame, ns-show-prefs): Don't add to global
          map.
        * term/common-win.el (x-setup-function-keys): Remove most of the
          keymappings.  Comment on the remaining ones.

When a file contains only the following:

    > cat -vte foo.txt
    foo$
    $
    bar$
    >

Moving the point to the beginning of the second line displays the
following in my emacs -nw sessions:

    ,-----------------------------------------------------------
    |foo
    | #
    |bar
    |
    |-UU-:**--F1  foo.txt        All (2,0)      (Text) -----
    |
    `-----------------------------------------------------------

Emacs obviously thinks that point is at (2, 0) but moves the terminal
cursor to the _second_ column instead of the first, at the location of
the '#' character in the output shown above.

This only happens for empty lines, so I'm guessing it's something
related to the calculation of line length?  I will try to go backwards
in the commit history of the last 1-2 months to see when this first
started happening, but in the meantime I thought I should report this
here too.

This is all tested with...

In GNU Emacs 24.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.20.1)
 of 2010-11-16 on gkeramidas-glaptop
configured using `configure  '--prefix=/opt/emacs' '--infodir=/opt/emacs/info''

Important settings:
  value of $LC_ALL: el_GR.utf8
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: el_GR.utf8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Text

Minor modes in effect:
  iswitchb-mode: t
  cua-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
ESC [ > 8 3 ; 4 0 0 0 3 ; 0 c f o o RET RET b a r RET
ESC O A ESC O A ESC x r e p o r t - b u TAB RET

Recent messages:
("/opt/emacs/bin/emacs" "foo.txt")
Ido mode disabled
Loading vc...done
For information about GNU Emacs and the GNU system, type <f1> C-a.
(New file)
Loading vc-git...done
Loading vc-hg...done
Auto-saving...done

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr message sendmail rfc822 mml easymenu
mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mailabbrev mail-utils gmm-utils mailheader
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advice-preload ido paren iswitchb cua-base hl-line keramida-hooks
keramida-autoload keramida-lang keramida-keys edmacro kmacro keramida-ui
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