tl25 pretest start

[Karl Berry]

The repository for the TL25 pretest has been mostly populated, though
not all platforms have been updated yet. In particular, not Mac, though
I expect it will be ready soon. Most Unix platforms are there (not
netbsd or aarch64). Windows will be there with tomorrow's build.

I haven't yet incorporated all the change items for this year, but a
start at the list is here:
  https://tug.org/texlive/pretest.html

It may take a day or so for the current build (that is currently
running) to make it to the (TL pretest) mirrors, as listed here:
  https://tug.org/texlive/mirmon/
(More pretest mirrors are welcome.)

Corrections and additions welcome. Most importantly, please test the new
binaries when you can.

Normal package updates uploaded to CTAN will be installed in both the
pretest and the regular (tlnet) repository for a while.

The TL guide, various web pages, etc., are not yet updated. --thanks, karl.