[luatex] read external file without extension

[Herbert Voss]

I have adifferent behaviour between pdflatex and lualatex:

create any file _without an extension, eg foo, with contents bar :-)

\documentclass{minimal}
\begin{document}
\input{foo}
\end{document}

running it with pdflatex it is ok, but with lualatex:

This is LuaTeX, Version beta-0.70.2-2012052410 (TeX Live 2012)
  restricted \write18 enabled.
(./test.tex
LaTeX2e <2011/06/27>
LuaTeX adaptation of babel <v3.8m-luatex-1.5> and hyphenation patterns 
for engl
ish, dumylang, nohyphenation, loaded.
(/usr/local/texlive/2012/texmf-dist/tex/latex/base/minimal.cls
Document Class: minimal 2001/05/25 Standard LaTeX minimal class
) (./test.aux)

! LaTeX Error: File `foo.tex' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: tex)

Enter file name:

------------------------------------------------------------

With any extension it is fine.

Herbert