[tlbuild] next TL test build attempt

[Karl Berry]

Hi again everyone -- it would be worth trying another test build at your
convenience.  Still no commits please.

Have had some updates to newer library versions and luatex/mpost, thanks
to Peter and Luigi.  I think what we've got now is pretty close to what
we'll be building for TL'15.

Still no updates to asymptote and no news from John B, so don't bother
with that ...

thanks,
k