[doc] mark-sexp keybinding

[Jesper Harder]

In GNU Emacs 21.3.50.82 (i686-pc-linux-gnu, GTK+ Version 2.0.2)
 of 2004-03-02 on defun.localdomain

The manual should mention the alternative keybinding (`C-M-SPC') for
`mark-sexp'.

`C-M-@' requires almost acrobatic skills to type on a Danish keyboard,
so the alternative is very useful.

*** /home/harder/emacs/man/mark.texi.~1.23.~    Sat Feb 21 01:12:10 2004
--- /home/harder/emacs/man/mark.texi    Wed Mar  3 00:36:31 2004
***************
*** 303,308 ****
--- 303,309 ----
  Set mark after end of next word (@code{mark-word}).  This command and
  the following one do not move point.
  @item C-M-@@
+ @itemx address@hidden
  Set mark after end of following balanced expression (@code{mark-sexp}).
  @item M-h
  Put region around current paragraph (@code{mark-paragraph}).


*** /home/harder/emacs/man/programs.texi.~1.79.~        Sat Feb 21 01:12:10 2004
--- /home/harder/emacs/man/programs.texi        Wed Mar  3 00:40:39 2004
***************
*** 641,646 ****
--- 641,647 ----
  @item C-M-t
  Transpose expressions (@code{transpose-sexps}).
  @item C-M-@@
+ @itemx address@hidden
  Put mark after following expression (@code{mark-sexp}).
  @end table
  
***************
*** 701,706 ****
--- 702,708 ----
  at or after point and the mark.
  
  @kindex C-M-@@
+ @kindex address@hidden
  @findex mark-sexp
    To set the region around the next balanced expression in the buffer,
  use @kbd{C-M-@@} (@code{mark-sexp}), which sets mark at the same place