Fix bug with algebraic evaluation in tables.

There was a problem that complex fields need a pair of parenthesis
around them.  For example, if one field is "a a" and another field
is "a+b", multiplication of the two gave "a^3+b" instead of "a^3+a^2 b".
Now variable replacement puts extra parenthesis around values.

ChangeLog

@@ -1,5 +1,9 @@
 2008-04-13  Carsten Dominik  <dominik@science.uva.nl>
 
+	* lisp/org-table.el (org-table-make-reference): Extra parenthesis
+	around single fields, to make sure that algebraic formulas get
+	correctly interpreted by calc.
+
 	* lisp/org-mhe.el: Changed author name to Thomas Baumann.
 
 	* lisp/org-exp.el (org-export-preprocess-string): Renamed-from

lisp/org-table.el

@@ -2298,7 +2298,8 @@ LISPP means to return something appropriate for a Lisp list."
 	      elements
 	    (prin1-to-string (if numbers (string-to-number elements) elements)))
 	(if (equal elements "") (setq elements "0"))
-	(if numbers (number-to-string (string-to-number elements)) elements))
+	(if numbers (setq elements (number-to-string (string-to-number elements))))
+	(concat "(" elements ")"))
     (unless keep-empty
       (setq elements
 	    (delq nil