[tex-live] shell_escape extension patch

[Akira Kakuto]

Hi,

> I've already received word from Akira that he will be happy to add
> this functionality to W32TEX, so: could this be considered for
> addition in the next TeXLive as well?

In some programs (e.g., bibtex), shellenabledp becomes unresolved.
In such cases, I simply linked

/* shellenabledp.c
   for programs which need shellenabledp
*/
int shellenabledp = 0;

This surely is avoided by smarter way.

Thanks,
Akira