[O] Bug: symbol function's definition is null : signum [7.5]

[Sylvain Beucler]

When using S-<up> to modify a date with an our range in Org 7.5, I get
"symbol function's definition is null : signum".

E.g. <2011-03-10 jeu. 10:30-11:30>

It appears that (org-modify-ts-extra) is using this function, but
unlike in CL isn't not an elisp built-in :)

As a work-around I added an internal defun:
(defun org-modify-ts-extra (s pos n dm)
  "Change the different parts of the lead-time and repeat fields in timestamp."
  (defun signum (x) 
    (cond
     ((> x 0)  1)
     ((< x 0) -1)
     ((= x 0)  0)))
[...]

-- 
Sylvain