[tlbuild] Backport tex4ht r671 to TL19

Tue Mar 10 17:05:55 CET 2020

Hi Henri (and all),

    Could you please backport the latest revision r671 of tex4ht to TL19?
    It contains an important fix for a regression that broke
    \usetikzlibrary.
    More info: https://puszcza.gnu.org.ua/bugs/?451

I've just now (finally) done this. tex4ht in TL2019 is now r54213.
It will take a day or two to make it around CTAN as usual.

I also updated tlnet-final (under tug.org/historic). --best, karl.