windows: provide filename in IOError exceptions
This brings the Windows posixfile errors in line with the errors
on other platforms.
#!/bin/sh
# http://mercurial.selenic.com/bts/issue352
"$TESTDIR/hghave" eol-in-paths || exit 80
hg init foo
cd foo
A=`printf 'he\rllo'`
echo foo > "$A"
hg add
hg ci -A -m m
rm "$A"
echo foo > "hell
o"
hg add
hg ci -A -m m
echo foo > "$A"
hg debugwalk
exit 0