Updated to 1.58

1.58  28 May 2012
      Many thanks for Vadim Repin for numerous excellent bug reports!
      [FIXES]
      - Appended pdf revisions incorrectly incremented object generation numbers
        https://rt.cpan.org/Ticket/Display.html?id=76513
      - Appending pdf revisions was broken for non-linearized PDFs
        https://rt.cpan.org/Ticket/Display.html?id=76514
      - Allow multiple "startxref" statements in the last 1024 bytes -- unlikely, but possible
        https://rt.cpan.org/Ticket/Display.html?id=77508
      - Allow whitespace at the beginning of an indirect object (I think the PDF spec is
        ambiguous about this)
        https://rt.cpan.org/Ticket/Display.html?id=76512
      - Allow backspace character
        https://rt.cpan.org/Ticket/Display.html?id=76151
      [DOCUMENTATION]
      - mention $pdf->setPageContent($pagenum, $tree->toString());
        Leo Lapworth and http://cpanforum.com/posts/13228

(rhaen)