Ticket #3070: changes to files in nested .zip archives are lost.

How to reproduce:

Changes to the text file inside nested .zip file are lost.

echo "hello, world" >hello.txt
zip message.zip hello.txt
zip wrapper.zip message.zip
rm -v hello.txt message.zip

Using mc enter to wrapper.zip/message.zip and edit (F4) "hello.txt",
save, then exit mc.

unzip wrapper.zip
unzip message.zip

Result: changes were not saved to "hello.txt".
Expected result: changes are saved.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3070_zip_save_changes'

* 3070_zip_save_changes:
  Ticket #3070: changes to files in nested .zip archives are lost.