[tex-live] pdfetex the default engine

[Thomas Esser]

Even though it seems like a good idea to help people using broken code by
   \let\pdfoutput\undefined
I no longer think that we should do this.

\pdfoutput is not the only primitive added by pdftex and not everybody
checks for \pdfoutput. E.g. geometry does:

  \ifx\pdfpagewidth\@undefined\else
    \ifnum\pdfoutput=\@ne
      \Gm at setdriver{pdftex}%
    \fi
  \fi

This breaks badly if we \let\pdfoutput\undefined.

So, really, I think that it is (to some extend) ok that bad code breaks,
but we should not make dirty hacks that breaks existing good code.

For teTeX, I have checked all macro packages by looking at every single
file that uses \pdfoutput. changebar still needs to be fixed, ltnews.cls
(not that important, I think) needs to be fixed and texinfo is fixed.
Everything else (in teTeX) looks ok. Maybe, someone should do the same
check for TeX Live.

Thomas