bug#870: Repeatable instance of bug#870

[martin rudalics]

>> As normal visiting of ChangeLog.870 doesn't have the problem
>> but revisiting it causes the problem, I think the bug is in
>> Finsert_file_contents; perhaps in the handling of REPLACE.
>> I'll have a look at it.
>
> I fixed the bug.  Actually what wrong was decode_coding_*
> but in the different place as above.

Handa-san, while you're there could you please also have a look at
bug#1039?  Maybe it's related to the present issue.

Thank you, martin.