[luatex] \readline issue

[Joseph Wright]

Hello all,

Reading in some UTF-8 input, I stumbled across some unexpected 
behaviour. With the demo file

\iffalse μΜ\fi
\newread\tmpread
\openin\tmpread \jobname %
\read\tmpread to \temp
\show\temp
\edef\temp{\detokenize\expandafter{\temp}}
\show\temp
\closein\tmpread
\openin\tmpread \jobname %
\readline\tmpread to \temp
\show\temp
\bye

runnign with LuaTeX (Version beta-0.76.0-2013061817 (rev 4627)) I get 
the terminal output

 > \temp=macro:
->\iffalse μΜ\fi .
l.5 \show\temp

?
 > \temp=macro:
->\iffalse μΜ\fi .
l.7 \show\temp

?
 > \temp=macro:
->\iffalse μΜ\fi
.
l.11 \show\temp

while for XeTeX I get the more expected:

 > \temp=macro:
->\iffalse μΜ\fi .
l.5 \show\temp

?
 > \temp=macro:
->\iffalse μΜ\fi .
l.7 \show\temp

?
 > \temp=macro:
->\iffalse μΜ\fi^^M.
l.11 \show\temp

Clearly something is up with the symbols: is this expected or a bug? 
(It's not restricted to the micro symbol, btw.)
--
Joseph Wright