[tex4ht] xmllint calls, so many

[Michal Hoftich]

> Maybe instead of doing system calls to xmllint one could record the
> file list into some file (maybe the .fls file produced by the
> -recorder option is OK for that), and then one would do something like
> this to make the syntax checking.
>
> awk '/^OUTPUT.*\.xml$/ { $1 =""; print}' record_file.fls | xargs xmllint
>
> We should anyway have some test target in the root makefile. That
> could be part of it.

Maybe we should instead test log files for errors. I've added a new
script, checklog.lua to the /lit directory. It can be used in the
following way:

texlua checklog.lua <filename>.log

I've added it to a few places in the Makefile.

Regarding proper tests, Deimi created a test suite:
https://github.com/dgalcius/t-tex4ht

It would be nice to update it a bit and incorporate into the build process.

Best,
Michal