Apparent bug in pdftex/xetex (but not luatex)

[Karl Berry]

Hi Marcel - thanks for the patch.

    +     name_field=18..19 means \scantokens pseudo files

I can't research right now, seems like that implies that in original TeX
(where there is no \scantokens), it should start at 18? I wrote that new
bit of code originally in response to the prior bug reports about
(original) TeX crashing with "e".

    +#elif defined(MF)
    +    if (inputstack[is_ptr].namefield <= 2) {

Good.

    +#else
    +#error "Unable to identify program"
    +#endif

MetaPost ... --thanks, karl.