[tldoc] kpathsea case-insensitive change

[Karl Berry]

Sorry everyone, but I forgot to write the item about Kpathsea now doing
case-insensitive filename matching in some cases. Since it's the most
incompatible thing that's been done with kpathsea in ages :(, I think we
have to tweak the doc again. Here is what I just wrote (and committed)
in the English ... please update your translations and commit/email me
as before? --thanks, karl.

--- texlive-en.tex	(revision 47347)
+++ texlive-en.tex	(working copy)
@@ -3684,6 +3684,11 @@
 \subsection{Present---2018}
 \label{sec:tlcurrent}
 
+Kpathsea: Case-insensitive filename matching now done by default in
+non-system directories; set \code{texmf.cnf} or environment variable
+\code{texmf\_casefold\_search} to~\code{0} to disable.
+Full details in the Kpathsea manual (\url{http://tug.org/kpathsea}).
+
 ep\TeX, eup\TeX: New primitive \cs{epTeXversion}.
 
 Lua\TeX: Preparation for moving to Lua\TeX\ 5.3 in 2019: a binary