Hello,

I've write a patch (see attachment) to fix the
`org-babel--string-to-number` function.

In my opinion, if people write the data in the form `0001`, it means that
he wants to treat it as a string:

    > #+name: TBL
    > |   id | name   | age |
    > |------|--------|-----|
    > | 0001 | Apollo |  16 |
    > | 0002 | Bmw    |  16 |
    >
    > #+BEGIN_SRC emacs-lisp :results value pp :var tbl=TBL
    > (mapc 'print tbl)
    > #+END_SRC
    >
    > #+RESULTS:
    > : (("0001" "Apollo" 16)
    > :  ("0002" "Bmw" 16))

Qijian