luatex pdf inclusion

[Karl Berry]

Thanks to everyone who's tried out the pretest.

I should have mentioned one thing in particular to test: inclusion of
pdf images in luatex. A new library is being used for that -- pplib,
originally written by Pawel Jackowski. So there are probably bugs and
unexpected differences from the behavior of the poppler library used
previously. (Couldn't hurt to try inclusion of other image types either,
but pdf is the one that is new code.)

We hope to use pplib in xetex and pdftex in coming years too. --thanks, karl.