Minor change to tex-live.sty

[Karl Berry]

    after the comment to this post[1], I had a look at tex-live.sty and I'd
    like to make a suggestion: Retire alltt.sty and use fancyvrb.sty to
    [1] https://emacs.stackexchange.com/a/55943/12242

Seems to me it would be better to improve auctex -- if it can support
fancyvrb in whatever way is desired, seems like it could support alltt.
I confess I'm not inclined to mess with loaded packages because editor
XYZ supports one better than another. Feels like churn. --thanks, karl.