Make @0 reference the last data line in a table.

The last data line in a table is often a line with important data, for
example sums of a column.  In tables with varying length, the row
number of this line is constantly changing, which makes it hard to
write programs creating tables and then installing formulas.

This patch introduces @0 as a special reference to the last row, so
that @0$3 would be the field in the last row, 3rd column.

doc/org.texi

@@ -1781,7 +1781,8 @@ Org also uses another, more general operator that looks like this:
 
 @noindent
 Column references can be absolute like @samp{1}, @samp{2},...@samp{N},
-or relative to the current column like @samp{+1} or @samp{-2}.
+or relative to the current column like @samp{+1} or @samp{-2}.  As a special
+case, @samp{@@0} references the last data line in the table.
 
 The row specification only counts data lines and ignores horizontal
 separator lines (hlines).  You can use absolute row numbers

lisp/ChangeLog

@@ -1,3 +1,8 @@
+2008-12-12  Carsten Dominik  <carsten.dominik@gmail.com>
+
+	* org-table.el (org-table-get-specials): Make @0 reference the
+	last line in a table.
+
 2008-12-11  Carsten Dominik  <carsten.dominik@gmail.com>
 
 	* org.el (org-log-done): Fix docstring.

lisp/org-table.el

@@ -1897,7 +1897,8 @@ For all numbers larger than LIMIT, shift them by DELTA."
 	(beginning-of-line 2)
 	(setq l (1+ l)))
       (setq org-table-current-line-types (apply 'vector (nreverse types))
-	    org-table-dlines (apply 'vector (cons nil (nreverse dlines)))
+	    org-table-dlines (apply 'vector (cons (car dlines)
+						  (nreverse dlines)))
 	    org-table-hlines (apply 'vector (cons nil (nreverse hlines)))))))
 
 (defun org-table-maybe-eval-formula ()