[luatex] macros to invoke lua in LaTeX

[Arthur Reutenauer]

> Oh, great. The pdf prefix was very counter-intuitive in front of some
> primitives, such as \primitive indeed.

  If I remember correctly, the original idea was to add "pdf" in front
of all the primitives that were particular to pdfTeX, and it thus meant
"pdfTeX" and not "PDF", at least originally (am I right?)  But it is
indeed not the most intuitive naming convention.

	Arthur