some code fiddling on affected files
manual: use new lua filter "lua-crossrefs.lua" hacked from
https://github.com/rnwst/pandoc-lua-crossrefs as replacement for
tablenos which broke with pandoc 2.8.2 (get nicer output anyway);
fix "excode39.svg" data $ -> # to avoid shell processing;
document `ZBarcode_HaveGS1SyntaxEngine()`