Ticket #82: savannah: "save as" retains mode (take 2) provided by dborka
Suppose you have two files, foo and bar. Both files have 444 permissions.
Now edit foo and "Save". It can't save and instead prompt you to "Save As".
Enter bar. It will chmod bar to 644. If we don't touch touch existing file
permissions for "Save", I don't see why we should for "Save As".
Patch adds S_IWUSR only if different_filename and file does not exist yet.
For consistency, it's S_IWUSR not S_IWRITE.
Signed-off-by: Sergei Trofimovich <slyfox@inbox.ru>