[Dev-luatex] compile flags in luatex

[Karl Berry]

I imported the luatex web2c/convert with the native tooldir first arg to
TeX Live.  Can you please try luatex again now and see if it gets any
farther?  (I am so far behind on other things I didn't try it.)

I also declared loadpoolstrings in web2c/texmf.defines instead of having
to redundantly repeat it in the five or so other .defines files.  I
trust that's ok; if problems, let me know.

Thanks,
k