largefiles: add examination of exec bit in "hg status --rev REV" case
Before this patch, "hg status --rev REV" doesn't list largefiles up
with "M" mark, even if exec bit of them is changed, because
"lfilesrepo.status" doesn't examine exec bit in such case.
#require execbit
$ hg init repo
$ cd repo
$ echo foo > foo
$ chmod 644 foo
$ hg ci -qAm '644'
$ chmod 755 foo
$ hg ci -qAm '755'
reverting to rev 0
$ hg revert -a -r 0
reverting foo
$ hg st
M foo
$ hg diff --git
diff --git a/foo b/foo
old mode 100755
new mode 100644
$ cd ..