[luatex] Luatex primitive names

[Arthur Reutenauer]

> "Now I'd rather test for \directlua. *But* if some day Jonathan
> include Lua as a scripting language in XeTeX, things will be more
> complicated."

  The primitive doesn't need to be called \directlua :-)  It will have a
very different behaviour anyway: XeTeX will not use callbacks to hook
Lua code into the TeX engine, it will simply enable to write Lua
programs inside TeX (Jonathan said so).

  But I guess that brings us back to the prefix issue, and maybe we can
rename \directlua to \luadirect (which will be coherent with the change
in the syntax anyway).  Taco?

	Arthur