quaziquoting

Hi
I modified the parser s-expressions to add the ability to use ` as equivalent to (quote
Hope this is useful.

Test: 

    $sexp = new Sexp();
    $arr = $sexp->parse("(quote (a `b `c 'dddddd' `|dGVzdA==| `(`#DEADBEEF `f g
    ;; wefewfew
    ) h) i)");
    print_r($arr);
    print_r($sexp->serialize($arr));

Output:

    (quote 
      (a 
        (quote b) 
        (quote c) dddddd 
        (quote test) 
        (quote 
          (
            (quote DEADBEEF) 
            (quote f) g) h)) i)


Glukhov Mikhail, Russia, St. Petersburg, 13.12.2012 10:21