bug#7934: 24.0.50; Nextstep: Can't copy and paste null characters

[Harald Hanche-Olsen <hanche@math.ntnu.no>]

Starting with .../Emacs.app/Contents/MacOS/Emacs -Q:
Type these characters in the *scratch* buffer:
abc C-q C-space def
so you now have a line looking like
abc^@def
with the ^@ representing a null character.
Now type the characters C-a C-k C-y
which should kill the line and then yank it back.

Expected result: The line is unchanged.
Actual result: Only the letters abc are yanked back.
The null character and the following characters are lost.

(I discovered this when I found myself unable to copy the debugger
buffer, which happened to contain bytecode snippets which had null
characters in them.)

In GNU Emacs 24.0.50.1 (x86_64-apple-darwin10.5.0, NS apple-appkit-1038.35)
 of 2011-01-21 on mack
Windowing system distributor `Apple', version 10.3.1038
configured using `configure  '--with-ns''

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

- Harald